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Background Sasanlimab is a monoclonal antibody that binds to the programmed cell death receptor 1 (PD-1). Anti-PD-1 monoclonal antibodies have improved patient clinical outcomes; however, not all treated patients derive clinical benefit. Further insights on potential biomarkers beyond PD-L1 expression levels would help to identify the patients most likely to respond to treatment. Objective This study evaluated tumor biopsies from patients treated with intravenous or subcutaneous sasanlimab to identify biomarkers of response and characterize pharmacodynamic activity. Methods Anti-PD-1/PD-ligand 1 (PD-L1)-naive patients with advanced solid tumors received sasanlimab intravenously at 1, 3, or 10 mg/kg every 3 weeks (n = 23) or subcutaneously at 300 mg every 4 weeks (n = 15). Best tumor percentage change from baseline was determined by RECIST. Whole-exome DNA and RNA sequencing were performed in tumor samples collected from treated patients at protocol-defined timepoints. PD-L1 and CD8 protein expression were evaluated in tumor biopsies by immunohistochemistry. Associations with response were assessed by linear regression analysis. Results Baseline tumor mutational burden (TMB), as well as PD-L1 and CD8 expression, were significantly associated with response to sasanlimab across the multiple dose levels, routes of administration, and range of tumor types evaluated. TMB is an independent biomarker from the various tumor inflammatory genes and signatures evaluated. Gene set enrichment analysis showed that higher baseline expression levels of genes related to the interferon-γ and PD-1 signaling pathways and the cell cycle were significantly associated with response to sasanlimab across tumor types. No differences were observed between routes of administration with regard to response to sasanlimab for the biomarkers of interest (TMB, PD-L1, CD8, and interferon-γ signature). Evaluation of pharmacodynamic changes showed increased tumor expression of genes enriched in adaptive immune response pathways. Conclusions Our findings indicate an active, immunomodulatory mechanism for the anti-PD-1 antibody sasanlimab across different tumor types and routes of administration. Trial Registration ClinicalTrials.gov identifier NCT02573259; registered October 2015. Supplementary Information The online version contains supplementary material available at 10.1007/s11523-021-00833-2.

BackgroundIvuxolimab (PF-04518600) and utomilumab (PF-05082566) are humanized agonistic IgG2 monoclonal antibodies against OX40 and 4-1BB, respectively. This first-in-human, multicenter, open-label, phase I, dose-escalation/dose-expansion study explored safety, tolerability, pharmacokinetics, pharmacodynamics, and antitumor activity of ivuxolimab+utomilumab in patients with advanced solid tumors.MethodsDose-escalation: patients with advanced bladder, gastric, or cervical cancer, melanoma, head and neck squamous cell carcinoma, or non-small cell lung cancer (NSCLC) who were unresponsive to available therapies, had no standard therapy available or declined standard therapy were enrolled into five dose cohorts: ivuxolimab (0.1–3 mg/kg every 2 weeks (Q2W)) intravenously plus utomilumab (20 or 100 mg every 4 weeks (Q4W)) intravenously. Dose-expansion: patients with melanoma (n=10) and NSCLC (n=20) who progressed on prior anti-programmed death receptor 1/programmed death ligand-1 and/or anti-cytotoxic T-lymphocyte-associated antigen 4 (melanoma) received ivuxolimab 30 mg Q2W intravenously plus utomilumab 20 mg Q4W intravenously. Adverse events (AEs) were graded per National Cancer Institute Common Terminology Criteria for Adverse Events V.4.03 and efficacy was assessed using Response Evaluation Criteria in Solid Tumors (RECIST) V.1.1 and immune-related RECIST (irRECIST). Paired tumor biopsies and whole blood were collected to assess pharmacodynamic effects and immunophenotyping. Whole blood samples were collected longitudinally for immunophenotyping.ResultsDose-escalation: 57 patients were enrolled; 2 (3.5%) patients with melanoma (0.3 mg/kg+20 mg and 0.3 mg/kg+100 mg) achieved partial response (PR), 18 (31.6%) patients achieved stable disease (SD); the disease control rate (DCR) was 35.1% across all dose levels. Dose-expansion: 30 patients were enrolled; 1 patient with NSCLC achieved PR lasting >77 weeks. Seven of 10 patients with melanoma (70%) and 7 of 20 patients with NSCLC (35%) achieved SD: median (range) duration of SD was 18.9 (13.9–49.0) weeks for the melanoma cohort versus 24.1 (14.3–77.9+) weeks for the NSCLC cohort; DCR (NSCLC) was 40%. Grade 3–4 treatment-emergent AEs were reported in 28 (49.1%) patients versus 11 (36.7%) patients in dose-escalation and dose-expansion, respectively. There were no grade 5 AEs deemed attributable to treatment. Ivuxolimab area under the concentration–time curve increased in a dose-dependent manner at 0.3–3 mg/kg doses.ConclusionsIvuxolimab+utomilumab was found to be well tolerated and demonstrated preliminary antitumor activity in selected groups of patients.Trial registration numberNCT02315066.

P-cadherin is a cell-cell adhesion molecule that is overexpressed in several solid tumors. PF-06671008 is a T-cell–redirecting bispecific antibody that engages both P-cadherin on tumors and CD3ϵ on T cells and induces antitumor activity in preclinical models. We conducted a phase 1, open-label, first-in-human, dose-escalation study to characterize the safety and tolerability of PF-06671008, towards determining the recommended phase 2 dose. Adult patients with treatment-refractory solid tumors received PF-06671008 (1.5–400 ng/kg) as a weekly intravenous (IV) infusion on a 21-day/3-week cycle. Parallel cohorts evaluated dosing via subcutaneous injection (SC) or an IV-prime dose. Of the 27 patients enrolled in the study, 24 received PF-06671008 IV in escalating doses, two received SC, and one IV-prime. A dose-limiting toxicity of cytokine release syndrome (CRS) occurred in the 400-ng/kg IV group, prompting evaluation of SC and IV-prime schedules. In all, 25/27 patients who received PF-06671008 reported at least one treatment-related adverse event (TRAE); the most common were CRS (21/27), decreased lymphocyte count (9/27), and hypophosphatemia (8/27). Seven patients permanently discontinued treatment due to adverse events and no treatment-related deaths occurred. Cytokine peak concentrations and CRS grade appeared to positively correlate with Cmax. Although the study was terminated due to limited antitumor activity, it provides important insights into understanding and managing immune-related adverse events resulting from this class of molecules.Clinical Trial RegistrationURL: https://clinicaltrials.gov/ct2/show/NCT02659631, ClinicalTrials.gov Identifier: NCT02659631.

BackgroundEvorpacept is a high affinity, CD47-blocking, myeloid checkpoint inhibitor (CPI) with an inactive Fc region designed to safely enhance anticancer therapeutics.1-3 In combination with standard chemotherapy and antibody regimens, evorpacept was evaluated in patients with advanced HNSCC or HER2-positive GC.MethodsPatients with untreated advanced HNSCC or previously treated HER2-positive GC received evorpacept (E) 10 mg/kg QW or 15 mg/kg QW in combination with pembrolizumab (P) + 5FU (F) + cisplatin or carboplatin (C) as 1st line therapy, or in combination with trastuzumab (T) + ramucirumab (R) + paclitaxel (P) as ≥2nd line treatment. The primary endpoint was first-cycle dose limiting toxicity (DLT). Tumor response, pharmacokinetic, and pharmacodynamic markers were assessed in all patients. Data from fully-enrolled HNSCC and GC cohorts, and follow-up data from patients with HNSCC administered EP are reported as of 15Jun2021.ResultsForty-one patients fully enrolled the following study cohorts: Thirteen patients with 1L HNSCC received EPFC. No DLTs were reported and the evorpacept maximum administered dose (MAD) was 15 mg/kg QW. Thirteen patients experienced an AE, 2 patients experienced treatment-related AEs (TRAE) of pneumonitis, anemia, fatigue, neutropenia, and hypersensitivity reaction (each n=1, 7.7%). Of 13 evaluable patients, 1CR/4PR/6SD (ORR 38.5%), mPFS 5.6 mo [3.6,NR], mOS not reached, and estimated 12-month OS of 83.3% were reported. Survival follow-up of 10 patients with CPI naïve HNSCC administered EP (2nd or later-line; ORR 40%) demonstrated a mPFS 4.6 mo [0.5,7.5], mOS 24.5 mo [3.1,NR] and estimated 12-month OS of 80%.Eighteen patients with ≥2L GC received ETRP. No DLTs were reported and the evorpacept MAD was 15 mg/kg QW. All patients experienced an AE, 8 patients experienced TRAEs, where the most common were urticaria, rash, and diarrhea (each n=3, 17%), fatigue and pruritus (each n=2, 11%). Of 18 evaluable patients, there were 1CR/12PR/3SD (ORR 72.2%; mDOR unreached) with a mPFS 9.8 mo [5.4,NR], mOS not reached, and estimated 12-month OS of 77.7%.ConclusionsInitial data suggest evorpacept is well tolerated with no DLTs in combination with the antibody/cytotoxic chemotherapy regimens evaluated above and a MAD of 15 mg/kg QW. Consistent with standard CPI therapeutic agents, the initial response benefit seen with evorpacept in combination is notably magnified in longer term PFS and OS endpoints in both the HNSCC and GC populations. Evorpacept’s preliminary positive impact on critical survival endpoints compares favorably with historical standards and warrants further evaluation in patients with HNSCC and GC.AcknowledgementsWe would like to thank all of the participating patients, their families and site research teams.Trial RegistrationClinicalTrials.gov identifier NCT03013218.ReferencesKauder S, et al. ALX148 blocks CD47 and enhances innate and adaptive antitumor immunity with a favorable safety profile. PLoS ONE 2018;13(8).Chow L, et al. A phase I study of ALX148, a CD47 blocker, in combination with standard anticancer antibodies and chemotherapy regimens in patients with advanced malignancy. Journal of Clinical Oncology 2020;38:15_suppl, 3056–3056.Chung H et al, ASPEN-01: A Phase 1 study of ALX148, a CD47 blocker, in combination with trastuzumab, ramucirumab and paclitaxel in patients with 2nd line HER2-positive advanced gastric or gastroesophageal junction (G/GEJ) cancer. ESMO-GI 2021; #SO-31.Ethics ApprovalThe study was approved by all participating institutions’ Ethics and/or Review Boards

Background CD47 is a myeloid checkpoint up-regulated by tumors to evade the anticancer immune response. ALX148 is a high affinity CD47-blocking fusion protein with an inactive Fc region designed to safely enhance anticancer therapeutics.1 2 ALX148 in combination with standard chemotherapy and antibody regimens was evaluated in patients (pts) with advanced HER2-positive GC or HNSCC. Methods Pts with previously treated advanced HER2-positive GC or untreated advanced HNSCC received ALX148 (A) 10 mg/kg QW or 15 mg/kg QW in combination with trastuzumab (T) + ramucirumab (ram) + paclitaxel (pac) as 2nd or later-line treatment or pembrolizumab (P) + 5FU + platinum (cisplatin or carboplatin) as 1st line therapy, respectively. The primary endpoint was dose limiting toxicity (DLT). Tumor response, pharmacokinetic (PK), and pharmacodynamic (PD) markers were assessed in all pts. Preliminary data from enrolling cohorts, and follow-up data from pts with GC administered A+T, and with HNSCC administered A+P are also reported as of 30June2020. Results Fifty-five pts enrolled into this portion of the study. Twelve patients with ≥2L GC received A+T+ram+pac and were evaluated for safety. No DLTs, were reported, and the ALX148 maximum administered dose was 15 mg/kg QW. Out of the 9 pts who experienced any adverse event, 7 pts reported treatment-related adverse events (TRAE). The most common TRAEs were low grade diarrhea, fatigue, pruritus and rash (each n=2,17%). Nine of the 12 patients were response-evaluable and reported a 66% ORR with 6PR and 3SD (including one ongoing near PR, ↓29.6%). Three patients with 1L HNSCC were administered A+P+5FU+platinum. No DLTs were reported and accrual to 15 mg/kg QW continues. Three pts experienced any AE, none were treatment-related. Of 3 evaluable patients with HNSCC, 2PR and 1SD were reported. Initial ALX148 combination PK and CD47 target occupancy are similar to that of single agent administration. Response duration and survival follow-up of 19 pts with HER2-positive GC administered A+T (2nd or later-line; 21% ORR) and of 10 pts with checkpoint inhibitor naive HNSCC administered A+P (2nd or later-line; 40% ORR) will be reported. Results of all cohorts will be updated at time of presentation. Conclusions Initial data suggests the myeloid checkpoint inhibitor, ALX148, is well tolerated in combination with the above anticancer antibodies, T-cell checkpoint inhibitor, and cytotoxic chemotherapy regimens with early anticancer signals in GC and HNSCC that compare favorably with historic controls. No MTD has been reached in any combination to date and accrual to chemotherapy combination regimens is ongoing. Trial Registration ClinicalTrials. gov identifier NCT03013218 Ethics Approval The study was approved by all participating institutions’ Ethics and/or Review Boards References Kauder S, Kuo T, Harrabi O, Chen A, Sangalang E, et al. ALX148 blocks CD47 and enhances innate and adaptive antitumor immunity with a favorable safety profile. PLoS ONE 2018;13(8). Chow L, Gainor J, Lakhani N, et al. A phase I study of ALX148, a CD47 blocker, in combination with standard anticancer antibodies and chemotherapy regimens in patients with advanced malignancy. Journal of Clinical Oncology 2020;38:15_suppl, 3056–3056.

This first-in-human study assessed safety, immunogenicity, pharmacokinetics, and pharmacodynamics of RN909, a monoclonal antibody antagonist of the glucagon receptor, in type 2 diabetes (T2DM) subjects. This study enrolled 84 T2DM subjects receiving stable metformin regimens. Forty-four subjects were randomized to receive single escalating doses of RN909 (0.3 to 6 mg/kg subcutaneously (SC), or 1 mg/kg intravenously (IV)), or placebo; 40 subjects were randomized to receive multiple escalating doses (50 to 150 mg SC) or placebo every 4 weeks for 12 weeks. RN909 was well tolerated; treatment-related elevated liver function tests (LFTs) were observed in 4/33 (12.1%) and 5/32 (15.6%) subjects treated with single and multiple doses, respectively, versus 1/10 (10%) and 0 in the respective placebo groups. RN909 dose-normalized AUCinf increased more than dose-proportionally following single SC doses, and after multiple doses, accumulation ratios ranged from 1.3 to 3.4. The incidence of antidrug antibodies (ADA) was 33% after single doses and 50% after multiple doses. RN909 produced dose-dependent, durable fasting plasma glucose (FPG)-lowering at day 29 (mean change −20.6 to −97.5 mg/dL) and day 85 (mean change; −27.2 to −43.5 mg/dL) after single and multiple doses, respectively. HbA1c also was reduced after single (mean change −0.30% to −1.44%), and multiple doses (−0.83% to −1.56%). RN909 was well tolerated after single and multiple doses in T2DM subjects, with diarrhea and elevated LFTs the most frequent adverse events. The appearance of ADA did not affect pharmacokinetics or efficacy. Robust lowering of FPG and HbA1c was observed.

Background: Evorpacept is a high affinity CD47-blocking fusion protein with an inactive human immunoglobulin Fc region designed to enhance the activity of other anti-neoplastic therapies, such as azacitidine (AZA), with minimal additional toxicity. Here, we present results from the phase 1 part of the ASPEN-02 study evaluating the safety and tolerability of evorpacept administered in combination with AZA in subjects with myelodysplastic syndrome (MDS). Methods: ASPEN-02 is a phase 1/2 open-label, multicenter study designed to evaluate the safety and tolerability and establish the recommended phase 2 dose (RP2D) of intravenous evorpacept in combination with AZA in phase 1 and to evaluate the efficacy of the combination of evorpacept + AZA compared to AZA alone in subjects with previously untreated higher risk MDS in phase 2. Adult subjects with newly diagnosed (ND) higher risk (IPSS-R>3.5) or relapsed/refractory (R/R) MDS were enrolled into phase 1 cohorts receiving escalating doses of evorpacept (20 mg/kg Q2W, 30 mg/kg Q2W, and 60 mg/kg Q4W) combined with AZA (75 mg/m 2 IV/SC x 7d) in a 28-day treatment cycle. The primary phase 1 endpoint is the frequency of first cycle dose-limiting toxicities (DLTs). The study is open for enrollment (NCT: NCT0441751). Results: As of July 15, 2021, 13 subjects were treated in phase 1 at evorpacept doses of 20 mg/kg Q2W (N=3), 30 mg/kg Q2W (N=3), and 60 mg/kg Q4W (N=7). Of the 7 ND subjects, 4 had therapy-related MDS, and 5 had TP53 mutation with complex cytogenetics. Of the 6 R/R subjects, all had received at least 1 prior hypomethylating agent (HMA)-based regimen. Median age of the phase 1 population was 74 years (range 56-82), and baseline ECOG scores were 0 (n=4) or 1 (n=9). No DLTs were observed in any cohort and a maximum tolerated dose (MTD) was not reached. All subjects experienced an adverse event. Treatment-related AEs (TRAEs) observed in >1 subject included constipation and infusion related reaction (n=3 each, 23%), and nausea and vomiting (n=2 each, 15%). Grade 3 or higher AEs of any causality occurring in >1 subject included febrile neutropenia (n=4; 31%), pneumonia (n=3, 23%), and anemia and thrombocytopenia (n=2 each, 15%). There was one Grade 3 or higher TRAE of transient neutropenia reported. There were no evorpacept-related serious adverse events (SAEs), no deaths on study, and no patients discontinued treatment due to an AE. Preliminary PK and PD data indicated dose-proportional pharmacokinetics consistent with prior studies, and evidence of full CD47 target occupancy (TO) in peripheral blood at both evorpacept peak and trough concentrations when administered every 2 or 4 weeks. Among the 5 ND subjects evaluable for response (all with TP53 mutation), there was 1 subject with a best response of marrow CR with hematologic improvement (HI), 2 subjects with cytogenetic response including 1 with HI, and 1 subject each with SD and PD. Of the 4 ND subjects who were transfusion dependent at baseline, 2 achieved transfusion independence. Among the 5 R/R subjects evaluable for response, there were 2 subjects with a best response of marrow CR, 2 with SD, and 1 with PD. Additional results will be presented at the meeting. Conclusions: The myeloid checkpoint inhibitor evorpacept was well tolerated in combination with AZA with an initial safety profile similar to that of AZA monotherapy. The evorpacept RP2D in combination with AZA is 60 mg/kg Q4W. Promising initial activity has been observed, with objective responses and hematologic improvement at multiple dose levels in subjects with both ND and R/R MDS, including those with adverse risk features such as TP53 mutation with complex cytogenetics, therapy-related MDS, and prior HMA-failure. This combination will be evaluated further in the randomized phase 2 part of this study. Disclosures Erba: AbbVie Inc: Other: Independent review committee; AbbVie Inc; Agios Pharmaceuticals Inc; Astellas; Bristol Myers Squibb; Celgene, a Bristol Myers Squibb company; Daiichi Sankyo Inc; Genentech, a member of the Roche Group; GlycoMimetics Inc; Incyte Corporation; Jazz Pharmaceuticals Inc; Kura Oncology; Nov: Other: Advisory Committee; AbbVie Inc; Agios Pharmaceuticals Inc; ALX Oncology; Amgen Inc; Daiichi Sankyo Inc; FORMA Therapeutics; Forty Seven Inc; Gilead Sciences Inc; GlycoMimetics Inc; ImmunoGen Inc; Jazz Pharmaceuticals Inc; MacroGenics Inc; Novartis; PTC Therapeutics: Research Funding; AbbVie Inc; Agios Pharmaceuticals Inc; Bristol Myers Squibb; Celgene, a Bristol Myers Squibb company; Incyte Corporation; Jazz Pharmaceuticals Inc; Novartis: Speakers Bureau. Altman: Loxo: Research Funding; Biosight: Membership on an entity's Board of Directors or advisory committees, Other: reimbursement for travel, Research Funding; Kura Oncology: Membership on an entity's Board of Directors or advisory committees, Research Funding; Kartos Therapeutics: Research Funding; ImmunoGen: Research Funding; Glycomimetics: Other: data monitoring committee; Fujifilm: Research Funding; Aprea: Research Funding; Aptos: Research Funding; Astellas: Honoraria, Research Funding; Boehringer Ingelheim: Research Funding; Celgene: Research Funding; ALX Oncology Inc.: Research Funding; Abbvie: Honoraria, Research Funding; Amgen: Research Funding; Syros: Membership on an entity's Board of Directors or advisory committees. Sayar: BMS: Honoraria. Scott: Bristol Myers Squibb: Consultancy, Honoraria, Research Funding. Fong: ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company; Abbvie: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Guan: Nektar Therapeutics: Current equity holder in publicly-traded company, Ended employment in the past 24 months; ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company; Pharmacyclics: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Jin: ALX Oncology Inc.: Consultancy; Tallac Therapeutics, Inc.: Consultancy. Forgie: ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company; Pfizer: Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months, Ended employment in the past 24 months. Pons: ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Randolph: ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Byrne: Karyopharm: Research Funding.

BackgroundAnticancer immunity relies on the release of tumor antigens and subsequent activation of the innate and adaptive immune systems. After cytotoxic chemotherapy induces neoantigen release, myeloid checkpoint inhibitors can help potentiate innate immune cell activity including antigen presentation. CD47 is a marker of self that interacts with SIRPα on myeloid immune cells and is upregulated by tumors to evade immune responses. Evorpacept is a high affinity CD47-blocking fusion protein with an inactive Fc region designed to safely enhance standard anticancer therapeutics. Pembrolizumab, a T cell checkpoint inhibitor that activates cytotoxic lymphocytes, is a standard option for patients with previously untreated recurrent/metastatic (R/M) HNSCC, both as a monotherapy and in combination with 5FU + platinum. Through increased activation of the immune system, a combination of evorpacept + pembrolizumab + 5FU/platinum might have more anti-tumor activity in R/M HNSCC than current standard therapeutic approaches. This combination approach could be particularly beneficial to R/M HNSCC patients with low PD-L1 expression, where anti-PD-(L)1 therapy historically has diminished efficacy. The combination of evorpacept + pembrolizumab + 5FU/platinum has undergone preliminary testing in the ongoing Phase 1 ASPEN-01 study,1 demonstrating initial clinical response and tolerability. In previously untreated, PD-L1-unselected R/M HNSCC patients treated with evorpacept + pembrolizumab + 5FU/platinum, patients experienced objective responses, including complete response. The ASPEN-04 study will assess the efficacy and safety of evorpacept in combination with pembrolizumab and chemotherapy in previously untreated patients with PD-L1-unselected R/M HNSCC.MethodsASPEN-04 (figure 1) is an ongoing non-comparative, open-label, randomized Phase 2 global study of evorpacept + pembrolizumab + chemotherapy (5FU + either carboplatin or cisplatin) or pembrolizumab + chemotherapy in patients with PD-L1-unselected metastatic or unresectable recurrent HNSCC who have not yet been treated for their advanced disease. After an initial safety lead-in cohort, ~106 patients will be randomized to receive evorpacept + pembrolizumab + chemotherapy or pembrolizumab + chemotherapy. Minimization factors used to randomize patients include geography, PD-L1 combined positive score, and HPV (p16) status. Patients in the evorpacept treatment arm will receive evorpacept 45 mg/kg IV Q3W. All patients will receive pembrolizumab 200 mg IV Q3W (maximum of 35 cycles) and standard administration of 5FU and platinum agents. The primary endpoint in this Simon two-stage trial design is objective response rate using RECIST v1.1. Key secondary endpoints include duration of response, progression-free survival, overall survival, and safety. Exploratory endpoints will characterize pharmacodynamic properties.Abstract 433 Figure 1ASPEN-04 Study SchemaAcknowledgementsWe would like to thank all the participating patients, their families, and site research teams.Trial RegistrationClinicalTrials.gov identifier, NCT04675333ReferencesKeun-Wook Lee, Hyun Cheol Chung, Won Seog Kim, et al. ALX148, a CD47 blocker, in combination with standard chemotherapy and antibody regimens in patients with gastric/gastroesophageal junction (GC) cancer and head and neck squamous cell carcinoma (HNSCC); ASPEN-01. Poster presented at: Society for Immunotherapy of Cancer Annual Meeting; November 2020.Ethics ApprovalThe study was approved by all participating institutions’ Ethics and/or Review Boards.

BackgroundBoth innate and adaptive immune responses are important components of anticancer immunity. CD47 is a marker of self that interacts with SIRPα on myeloid immune cells, inhibiting their function. CD47 is upregulated by tumors to evade immune responses and its expression is associated with poor prognosis. Evorpacept is a high affinity CD47-blocking fusion protein with an inactive Fc region designed to be safely combined with and to enhance the efficacy of standard anticancer therapeutics. Evorpacept used in combination with pembrolizumab has the potential to augment both innate and adaptive anti-tumor immune responses. As an antibody inhibiting PD-1/PD-L1 signaling in the T cell immune checkpoint, pembrolizumab has demonstrated anti-tumor efficacy through activation of tumor-infiltrating lymphocytes. Pembrolizumab as a single agent is a standard treatment option for patients with previously untreated recurrent or metastatic (R/M) HNSCC with PD-L1-positive (combined positive score [CPS] ≥1) tumors. The combination of evorpacept + pembrolizumab has shown preliminary efficacy and acceptable tolerability in initial results available from the cohort of patients with ≥2nd line advanced HNSCC in the ongoing Phase 1 ASPEN-01 study.1 PD-L1-unselected patients who had not received prior checkpoint inhibitor treatment were treated with evorpacept + pembrolizumab and experienced a 40% ORR and 4.6 months median PFS, comparing favorably with historical controls. Based on these encouraging results, the ASPEN-03 study will assess the efficacy and safety of evorpacept in combination with pembrolizumab in previously untreated patients with metastatic or unresectable recurrent PD-L1 positive HNSCC.MethodsASPEN-03 (figure 1) is an ongoing non-comparative, open-label, randomized Phase 2 global study of evorpacept + pembrolizumab or pembrolizumab alone in patients with metastatic or unresectable recurrent, PD-L1-positive (CPS ≥1) HNSCC who have not yet been treated for their advanced disease. After an initial safety lead-in cohort, ~105 patients will be randomized 2:1 to receive evorpacept + pembrolizumab or pembrolizumab alone. Minimization factors used to randomize patients include geography, CPS, and HPV (p16) status. Patients in the evorpacept + pembrolizumab treatment arm will receive evorpacept 45 mg/kg IV Q3W. All patients will receive pembrolizumab 200 mg IV Q3W (maximum of 35 cycles). The primary endpoint in this Simon two-stage trial design is objective response rate using RECIST v1.1. Key secondary endpoints include duration of response, progression-free survival, overall survival, and safety. Exploratory endpoints will characterize pharmacodynamic properties.Abstract 439 Figure 1ASPEN-03 study schemaAcknowledgementsWe would like to thank all the participating patients, their families, and site research teams.Trial RegistrationClinicalTrials.gov identifier, NCT04675294ReferencesKeun-Wook Lee, Hyun Cheol Chung, Won Seog Kim, et al. ALX148, a CD47 blocker, in combination with standard chemotherapy and antibody regimens in patients with gastric/gastroesophageal junction (GC) cancer and head and neck squamous cell carcinoma (HNSCC); ASPEN-01. Poster presented at: Society for Immunotherapy of Cancer Annual Meeting; November 2020.Ethics ApprovalThe study was approved by all participating institutions’ Ethics and/or Review Boards.

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with most patients relapsing even after initial therapies. Despite recent advances in treatment, the development of efficacious novel treatments remains an unmet need. CD47 is a myeloid checkpoint upregulated by tumor cells to evade the host immune response, and its blockade enhances anti-tumor immunity (Weiskopf, 2017). Recently, pre-clinical and clinical studies that explored the use of CD47 targeting agents in combination with azacitidine, a hypomethylating chemotherapeutic, demonstrated robust anti-cancer activity (Feng, ASH 2018 and Sallman, ASH 2019). ALX148 is an engineered fusion protein comprised of a high affinity CD47 blocker linked to an inactive human immunoglobulin Fc region. In preclinical studies, ALX148 bridges innate and adaptive immunity by promoting macrophage phagocytosis, dendritic cell activation and a shift of tumor-associated macrophages towards an inflammatory phenotype, leading to increased anti-tumor activity when combined with various anti-cancer therapeutics (Kauder, 2018). ALX148 has previously been shown to be well tolerated in patients with both solid tumor and hematological malignancies with encouraging anti-tumor responses reported in combination with anti-cancer therapeutics (EHA 2020, #EP1247 and ASCO 2020, #3056). Recently, the combination of azacitidine with venetoclax, a BCL2 inhibitor, has shown increased efficacy compared to azacitidine alone in patients with AML (EHA 2020, #LB2601). We observed in vitro treatment with azacitidine or venetoclax increased the cell surface expression of both CD47 and calreticulin, a pro-phagocytic marker, in multiple AML cell lines. We thereby hypothesize that combining ALX148 with either azacitidine or venetoclax would enhance the therapeutic efficacy against AML and report our preclinical findings here. In vitro treatment with ALX148 led to enhanced phagocytic engulfment by human monocyte-derived macrophages across multiple AML cell lines treated with azacitidine or venetoclax, including those harboring TP53 and FLT3 mutations, compared to either treatment alone. Our in vitro findings correlated with enhanced in vivo antileukemic activity in several murine AML xenograft models. Mice were inoculated via tail vein or implanted subcutaneously with AML cells, and when tumors reached exponential growth, mice were randomized to receive the following: vehicle control, azacitidine, venetoclax, ALX148 alone or ALX148 in combination. Cohorts receiving ALX148 combination therapies demonstrated significantly greater inhibition of tumor progression with evidence of tumor eradication, leading to markedly enhanced survival over any single agent therapy. Together, these in vitro and in vivo results provide rationale that ALX148 combinations may benefit AML and MDS patients. Clinical trials with ALX148 in patients with MDS (NCT04417517) and AML are currently planned. Disclosures Chen: ALX Oncology: Consultancy, Current equity holder in publicly-traded company, Ended employment in the past 24 months; Tallac Therapeutics: Current Employment, Current equity holder in private company. Harrabi:ALX Oncology Inc: Consultancy, Current equity holder in publicly-traded company, Ended employment in the past 24 months; Tallac Therapeutics: Current Employment, Current equity holder in private company. Fong:ALX Oncology Inc: Current Employment, Current equity holder in publicly-traded company. Ruffner:ALX Oncology Inc: Current Employment, Current equity holder in publicly-traded company. Forgie:ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company; Pfizer Inc.: Ended employment in the past 24 months. Sim:ALX Oncology Inc: Consultancy, Current equity holder in publicly-traded company, Ended employment in the past 24 months; Tallac Therapeutics: Current Employment, Current equity holder in private company. Randolph:ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company. Wan:Tallac Therapeutics: Current Employment, Current equity holder in private company; ALX Oncology Inc: Consultancy, Current equity holder in publicly-traded company, Ended employment in the past 24 months. Pons:ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company. Kuo:ALX Oncology Inc: Consultancy, Current equity holder in publicly-traded company, Ended employment in the past 24 months; Tallac Therapeutics: Current Employment, Current equity holder in private company.

Introduction: PF-06801591 is a humanized IgG4 monoclonal antibody that binds to the programmed cell death (PD-1) receptor and blocks its interaction with PD-1/2 ligands (PD-L1/2). In a phase 1 dose expansion study (NCT02573259), 106 patients with locally advanced or metastatic non-small cell lung cancer (NSCLC; n=68) or urothelial carcinoma (UC; n=38) were treated with PF-06891591 300 mg subcutaneously monthly. 12 patients with NSCLC (17.9%) and 7 with UC (18.4%) had a best overall response of partial response (PR). Response rates were higher in patients with high (≥1%) vs low ( Citation Format: Byoung Chul Cho, Konstantin Penkov, Igor Bondarenko, Joanna Pikiel, Hee Kyung Ahn, Alison Forgie, Ira Jacobs, Vinicius Bonato, Xinmeng Jasmine Mu, Keith Ching, Jeffrey Chou, Melissa L. Johnson. Molecular markers in a phase I dose expansion study of PF-06801591 in locally advanced or metastatic non-small-cell lung cancer and urothelial carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT138.

The B-cell maturation antigen (BCMA) is an attractive target in multiple myeloma since it is more selectively expressed on myeloma cells. Meanwhile, T-cell-engaging bispecific antibodies (BsAbs) are an important class of antibody therapeutics in cancer therapy. BCMA-CD3 BsAbs simultaneously bind to CD3 on T cells and BCMA on tumor cells, activate T cells, and redirect T cells' cytotoxicity against tumor cells. BCMA is shed from the surface of plasma cells by gamma-secretase-mediated cleavage, leading to detectable, soluble BCMA (sBCMA) in circulation. Higher concentrations of sBCMA in patients with myeloma are associated with poorer clinical outcomes. Furthermore, sBCMA in circulation may act as a drug sink, especially when it is present in a relatively higher amount compared to the drug concentration, potentially attenuating the intended pharmacological mechanism and impacting pharmacokinetics and efficacious dose predictions. To address the complexities, we leveraged a quantitative systems model to characterize the kinetics of a model BsAb, T-cell, cytokines and serum M-protein upon BsAb treatment based on the literature data. This model incorporated T-cell activation, cytokine profiles as well as serum M-protein following various dosing regimens and baseline sBCMA levels. This model could assist in the design of clinical dosing strategies for BCMA-CD3 BsAb programs. Citation Format: Chandrasekhar Udata, Dai Wei, Sibo Jiang, Alison Forgie, Andrea Hooper, Wenlian Qiao, Cynthia Musante, Donghua Yin. BCMA-CD3 bispecific antibodies: A modeling framework to characterize kinetics of bispecific antibody, T cell, cytokines, and serum M-protein [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5508.

Background The first-in-human, ongoing phase I study of PF-06801591, a humanized IgG4 antibody to programmed cell death 1 (PD-1) receptor, consisted of a Part 1 dose escalation and Part 2 dose expansion. In Part 1, PF-06801591 was administered intravenously or SC with an acceptable safety profile and antitumor activity in several solid tumor types. Herein, we report on Part 2 where we further evaluated SC PF-06801591 in patients (pts) with NSCLC and UC. Methods Anti-PD-1/L1-naive pts with NSCLC (n = 68) and UC (n = 38) received SC PF-06801591 300 mg q4w. NSCLC pts had ≤1 prior line of chemotherapy (CT) ± ≥1 ALK/EGFR mutation-directed therapies (if applicable) and UC pts had ≤2 lines of prior CT. Tumors were evaluated q8w by RECIST 1.1. Blood samples were collected for pharmacokinetic (PK) and immunogenicity assessments. Archival or baseline biopsies were evaluated by immunohistochemistry for PD-L1, RNA-seq, and whole exome sequencing. Results As of 27Dec2018, with median duration of treatment of 2.8 mos. in all 106 treated pts (55 still receiving treatment), 50.9% had treatment-related AEs (TRAEs) with 8.5% grade 3 or higher. Most common TRAEs were hyperthyroidism (9.4%), pruritus (6.6%), and increased amylase/lipase, anemia, hypothyroidism, pneumonitis, and rash (4.7% each). Treatment-emergent anti-drug antibodies were detected in 3 pts. With median follow-up of 5.1 mos. in 67 modified intent to treat (mITT) NSCLC pts, 11 (16.4%) pts achieved a partial response (PR) and 26 (38.8%) had stable disease (SD); the objective response rate (ORR) was 16.4% with 95% confidence interval (CI) 8.5-27.5% (25% in pts with ≥1% tumor cell PD-L1 expression). With median follow-up of 3.0 mos. in 37 mITT UC pts, 6 (16.2%) pts had a PR and 13 (35.1%) had SD; ORR was 16.2% (95% CI 6.2-32.0%). PK and biomarker data will be presented. Conclusions SC PF-06801591 given monthly was well tolerated, with minimal rates of injection site reactions and low incidence of immunogenicity. SC PF-06801591 demonstrated antitumor activity in NSCLC and UC pts at an early time point. The study is ongoing to further assess the durability of responses and long-term safety profile. Clinical trial identification NCT02573259. Editorial acknowledgement S. Mariani MD PhD of Engage Scientific Solutions, Southport, CT, funded by Pfizer and L. Chen. Legal entity responsible for the study Pfizer Inc. Funding Pfizer Inc. Disclosure B.C. Cho: Advisory / Consultancy, Research grant / Funding (institution): Novartis; Advisory / Consultancy, Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): MOGAM Institute; Research grant / Funding (institution): Dong-A ST; Research grant / Funding (institution), Licensing / Royalties: Champions Oncology; Advisory / Consultancy, Research grant / Funding (institution): Janssen; Advisory / Consultancy, Research grant / Funding (institution): Yuhan; Advisory / Consultancy, Research grant / Funding (institution): Ono; Research grant / Funding (institution): Dizal Pharma; Advisory / Consultancy, Research grant / Funding (institution): MSD; Advisory / Consultancy: Boehringer Ingelheim; Advisory / Consultancy: Roche; Advisory / Consultancy: BMS; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Eli Lilly; Advisory / Consultancy: Takeda; Shareholder / Stockholder / Stock options: TheraCanVac Inc; Shareholder / Stockholder / Stock options: Gencurix Inc; Shareholder / Stockholder / Stock options: Bridgebio Therapeutics. K. Penkov: Research grant / Funding (institution): AbbVie; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): MSD; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Prestige Biopharma; Research grant / Funding (institution): Regeneron; Research grant / Funding (institution): Tanvex. M. Korozan: Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Genentech/Roche; Research grant / Funding (institution): Regeneron. Y. Kulyaba: Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Azaya Therapeutics; Research grant / Funding (institution): Celltrion; Research grant / Funding (institution): GlaxoSmithKline; Research grant / Funding (institution): Janssen; Research grant / Funding (institution): Merck; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Regeneron; Research grant / Funding (institution): Roche; Research grant / Funding (institution): Synta Pharmaceuticals; Research grant / Funding (institution): Tanvex. H.K. Ahn: Honoraria (self): AstraZeneca; Honoraria (self): Boehringer Ingelheim; Honoraria (self): Eisai; Honoraria (self): Ono; Honoraria (self): Roche. S. Odintsova: Full / Part-time employment: Complete Medical Technologies. J. Davda: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer. A. Forgie: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer. X. Wang: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer. R. Li: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer. I.A. Jacobs: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer. F. Kazazi: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer. J. Chou: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer. M.L. Johnson: Honoraria (institution), Research grant / Funding (institution): AstraZeneca; Honoraria (institution), Research grant / Funding (institution): Genentech/Roche; Honoraria (institution), Research grant / Funding (institution): Boehringer Ingelheim; Honoraria (institution), Research grant / Funding (institution): Loxo; Honoraria (institution), Research grant / Funding (institution): Merck; Honoraria (institution), Research grant / Funding (institution): Mirati; Honoraria (institution), Research grant / Funding (institution): Sanofi; Honoraria (institution): Calithera; Honoraria (institution): Celgene; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): EMD Serono; Research grant / Funding (institution): Janssen; Research grant / Funding (institution): GenMab; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): AbbVie; Research grant / Funding (institution): StemCentrix; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Incyte; Research grant / Funding (institution): Array BioPharma; Research grant / Funding (institution): Regeneron; Research grant / Funding (institution): Adaptimmune; Research grant / Funding (institution): Amgen; Research grant / Funding (institution): Apexigen; Research grant / Funding (institution): BeiGene; Research grant / Funding (institution): BerGenBio; Research grant / Funding (institution): Birdie; Research grant / Funding (institution): Checkpoint Therapeutics; Research grant / Funding (institution): Corvus; Research grant / Funding (institution): Cytomx; Research grant / Funding (institution): Daiichi–Sankyo; Research grant / Funding (institution): Dynavax; Research grant / Funding (institution): G1 Therapeutics; Research grant / Funding (institution): Genocea; Research grant / Funding (institution): Gritstone; Research grant / Funding (institution): Hengrui Therapeutics; Research grant / Funding (institution): Lycera; Research grant / Funding (institution): Neovia; Research grant / Funding (institution): Syndax; Research grant / Funding (institution): Tarveda; Spouse / Financial dependant, contract lobbyist : Astellas; Spouse / Financial dependant, contract lobbyist : Otsuka Pharmaceuticals. All other authors have declared no conflicts of interest.

523 Background: PF-04518600 (PF-8600) is a humanized agonist IgG2 monoclonal antibody to the tumor necrosis factor superfamily receptor OX40. PF-8600 was given to patients (pts) with advanced/metastatic hepatocellular carcinoma (HCC) in dose expansion of a phase 1 study (NCT02315066). Safety and tolerability were primary endpoints and exploratory endpoints included biomarker analyses. Methods: Pts received either 30 mg (Arm 1) or 250 mg (Arm 2) of PF-8600 intravenously Q2W. Pts had pathologic diagnosis of advanced HCC, a Child-Pugh score of A or B7, and had ≤2 prior lines of therapy, or if treatment naïve, had declined standard of care. Radiological tumor assessments were conducted Q8W. Biopsy samples collected at baseline and wk 6 were analyzed by immunohistochemistry and RNA sequencing for pharmacodynamic (PD) analyses. Whole blood samples were collected longitudinally for DNA extraction for high-throughput sequencing of the T cell receptor β-chain. Results: Arm 1 enrolled 16 pts (mean age 65.6 yrs; range 54-81 yrs; prior PD-1/PD-L1: 5 pts) and Arm 2 enrolled 19 pts (mean age 61.7 yrs; range 26-79 yrs; prior PD-1/PD-L1: 3 pts). All grade treatment related adverse events (TRAEs) occurred in 69% of pts in Arm 1 and 58% of pts in Arm 2. The rate of ≥Grade 3 TRAEs was 31% and 16% in Arms 1 and 2, respectively. For both arms combined, the most common (≥10%) TRAEs were rashes and pruritus. In Arm 1, 8 pts (50%) and in Arm 2, 10 pts (53%) achieved stable disease (SD), with a mean duration of 18.4 (range: 14.0-30.3 wks) and 17.4 wks (range: 8.0-31.9 wks), respectively. PD effects were more evident in Arm 1 than Arm 2, including increased OX40 tumor expression and positive changes in gene signatures, reflecting an active anti-tumor immune response. Conclusions: PF-8600 was generally well tolerated and provided meaningful disease control. While safety and efficacy were not significantly different between the 2 doses, there were potential differences in the PD data. The safety and relative durability of SD in HCC pts may provide a rationale for exploration of combination therapy in this pt population. Clinical trial information: NCT02315066.

Introduction: PF-06863135 (PF-3135) is a bispecific, humanized, monoclonal antibody (mAb) consisting of BCMA- and CD3-targeting arms paired on an IgG2a backbone by hinge-mutation technology. PF-3135 binds BCMA+ myeloma cells and CD3+ T cells with affinities of 20 pM and ~40 nM, respectively (Panowski et al. Blood 2016). We report here findings from the dose-escalation portion of an ongoing, multi-center, open-label, phase I study (NCT03269136) of PF-3135 in patients with RRMM. Methods: Adult patients (≥18 years of age) with RRMM, previously treated with a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 mAb, received escalating, intravenous (IV) doses of PF-3135, once weekly. Prior BCMA-targeted bispecific T-cell engager or chimeric antigen receptor T-cell (CART) treatment was allowed by protocol. Patients had measurable disease per the International Myeloma Working Group (IMWG) updated criteria 2014. A modified toxicity probability interval method (mTPI), targeting a dose-limiting toxicity (DLT) rate of 25% (equivalence interval ± 5%) was used for dose escalation. The primary study objectives are to assess PF-3135 safety and tolerability, to determine the maximum tolerated dose (MTD) and select the recommended phase II dose (RP2D). Secondary objectives include evaluation of anti-myeloma activity, pharmacokinetics (PK), and immunogenicity of PF-3135. Results: As of April 9, 2019, 17 patients had received once weekly, non-continuous, IV infusion of PF-3135 in 6 dose-escalation groups. The majority were men (71%). The median age was 61 yrs (range, 47-82 yrs) and median disease duration since onset was 7 yrs (range, 1.1-13.3 yrs). Ten (59%) patients had ≥1 chromosomal abnormality and 5 (29%) had a normal karyotype (status not known for 2 [12%] patients). The median number of prior anti-myeloma therapies was 11; 5 (29%) patients had received prior BCMA-targeted therapy. Eight (47%) patients had relapsed MM and 8 (47%) had refractory disease (recurrence type not known for 1 [6%] patient). Ten (59%) patients experienced treatment-related (TR) AEs of any grade. Most TRAEs were grade 1-2, including cytokine release syndrome (CRS, 24%), thrombocytopenia (24%), anemia (18%), and pyrexia (18%). Three (18%) patients had grade 3 TRAEs (increased alanine aminotransferase/aspartate aminotransferase, leukocytopenia, neutropenia, and lymphopenia). One patient treated at the highest dose level, who had received prior BCMA CART therapy, developed treatment-related febrile neutropenia, a DLT, which may have been related to CRS and borderline/low neutrophil count at baseline. None of the patients had grade 4-5 TRAEs or discontinued treatment due to a TRAE. The median duration of treatment was 4 (range, 2-12) actual dosing days. Sixteen of the 17 patients were evaluable for response. At the time of data cut-off, one (6%) patient had a minimal response and 6 (35%) patients had stable disease (SD) across dose levels, as best response by investigator IMWG assessment; 9 (53%) patients experienced disease progression. The clinical benefit rate (defined as best response ≥SD) was 41% (95% CI: 18.4%, 67.1%). Conclusions: Treatment with IV PF-3135 was well tolerated at the dose levels evaluated. The observed CRS events were moderate and dose-dependent. Additional dose cohorts are accruing. The latest clinical, biomarker, and PK data will be presented for this ongoing study. Disclosures Raje: Medscape: Honoraria; Research to Practice: Honoraria; Takeda: Consultancy, Honoraria; Merck: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; AstraZeneca: Research Funding. Jakubowiak:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Consultancy, Honoraria; Juno: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; SkyLineDx: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; KaryoPharm Therapeutics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Gasparetto:Janssen: Consultancy, Honoraria, Other: Travel, accommodations, or other expenses paid or reimbursed ; BMS: Consultancy, Honoraria, Other: Travel, accommodations, or other expenses paid or reimbursed ; Celgene: Consultancy, Honoraria, Other: Travel, accommodations, or other expenses paid or reimbursed . Cornell:KaryoPharm: Consultancy; Takeda: Consultancy. Krupka:Pfizer: Employment, Equity Ownership. Navarro:Pfizer: Employment, Equity Ownership. Forgie:Pfizer: Employment, Equity Ownership. Udata:Pfizer: Employment, Equity Ownership. Basu:Pfizer: Employment, Equity Ownership. Chou:Pfizer: Employment, Equity Ownership. Leung:Pfizer: Employment, Equity Ownership. Lesokhin:BMS: Consultancy, Honoraria, Research Funding; Serametrix Inc.: Patents & Royalties; Takeda: Consultancy, Honoraria; Genentech: Research Funding; Juno: Consultancy, Honoraria; GenMab: Consultancy, Honoraria; Janssen: Research Funding. OffLabel Disclosure: PF-06863135, investigational agent

Introduction: PF-06801591 is a humanized IgG4 monoclonal antibody that binds to programmed cell death (PD-1) receptor, blocking its interaction with PD-1 ligands. In a phase I study (NCT02573259; dose-escalation) of 40 patients (pts) with multiple solid tumor types treated with PF-06891591 intravenously (IV) or subcutaneously (SC), 7 pts showed partial response. PF-06801591 was well tolerated at all doses. Biopsy samples were evaluated for predictive biomarkers and pharmacodynamic effects. Methods: Biopsy samples at baseline and on-treatment (IV:day 29; SC:day 36) were collected from 4 dose cohorts (IV:1, 3 and 10 mg/kg; SC:300 mg). Whole-exome sequencing (WES) and RNA-seq of biopsy tissue were used to estimate tumor mutation burden (TMB) and gene expression. Regression analysis was used to identify TMB/genes/pathways potentially associated with response in baseline tissue. Differential analysis of baseline and on-treatment biopsies identified genes/pathways potentially upregulated by PF-06801591. PD-L1 (clone SP-263; Ventana) expression was evaluated in tumor biopsies by immunohistochemistry (IHC) and pathologist scoring. Results: In a combined WES analysis of samples from baseline biopsies (all doses, n=24 pts), higher TMB was significantly associated with improved objective response (R^2=0.215, P=0.013). From RNA-seq analysis, genes positively associated with response were involved in interferon-gamma (IFNG) and PD-1 signaling, and cell cycle; CTLA4 was among the genes most significantly associated with response (P Conclusion: Based on a mixed set of tumor types with possible sensitivity to anti-PD-1, high TMB, IFNG signaling, and PD-L1 were associated with response to PF-06801591, as reported for other anti-PD-1 antibodies. Albeit based on a small sample size and diverse indication profile, baseline expression of CTLA4 appears to be highly associated with response and PD-L1 RNA levels may be better associated with response than protein expression by IHC. Increased expression of genes/pathways associated with adaptive immune activation in on-treatment biopsies indicates an active, immunomodulatory mechanism with anti-PD-1 therapy. This ongoing study will evaluate predictive biomarkers in dose-expansion cohorts of PF-06801591 in non-small cell lung cancer and urothelial cancer. Acknowledgments Study sponsor: Pfizer. Medical writing support: Chu Kong Liew (Engage Scientific Solutions), funded by Pfizer. Citation Format: Siwen Hu-Lieskovan, Fadi Braiteh, Juneko E. Grilley-Olson, Shobha Potluri, Xiao Wang, Alison Forgie, Vinicius Bonato, Jeffrey Chou, Melissa L. Johnson. Predictive biomarkers and pharmacodynamic changes in tumor RNA expression in a phase I study of anti PD-1 monoclonal antibody PF-06801591 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT046.

Importance We assessed feasibility of monthly subcutaneous administration of PF-06801591, a humanized immunoglobulin G4 monoclonal antibody that binds to the programmed cell death (PD-1) receptor and blocks its interaction with PD-1 ligands. Objective To evaluate the safety, efficacy, and pharmacokinetics of PF-06801591 administered intravenously vs subcutaneously. Design, Setting, and Participants Ongoing phase 1, open-label, multicenter, dose-escalation study of 40 patients, 18 years or older, with locally advanced or metastatic solid tumors, enrolled between March 8, 2016, and March 5, 2018, from 4 US medical centers. Interventions An intravenous dose of 0.5, 1, 3, or 10 mg/kg of PF-06801591 was administered every 3 weeks or a subcutaneous dose of 300 mg was administered every 4 weeks. Dose escalation occurred after 2 to 4 patients were enrolled per dose level, with additional patients enrolled in each cohort for further assessment. Main Outcomes and Measures The primary end points were dose-limiting toxic effects and safety. Secondary end points included pharmacokinetics, immunogenicity, PD-1 receptor occupancy, and efficacy. Results Of 40 enrolled patients (12 men and 28 women; mean [SD] age, 61 [13] years) in this phase 1 dose-escalation trial, 25 received PF-06801591 intravenously at escalating dose levels (0.5, 1, 3, or 10 mg/kg) and 15 patients received the monoclonal antibody subcutaneously at a single dose level. No dose-limiting toxic effects were observed. Grade 3 or higher treatment-related adverse events occurred in 4 (16%) patients treated intravenously and 1 (6.7%) patient treated subcutaneously. Immune-related adverse events occurred in 10 (40%) patients treated intravenously and 3 (20%) treated subcutaneously. No dose–adverse event associations were observed during intravenous dose escalation, and no serious skin toxic effects occurred with subcutaneous delivery. Responses were seen in 5 patients receiving PF-06801591 intravenously and in 2 patients treated subcutaneously for an overall objective response rate of 18.4%. Median overall survival was not reached with intravenous dosing vs 10.7 months with subcutaneous administration. Exposure to PF-06801591 increased in a dose-proportional manner over the range of intravenous doses. Median time to maximum observed serum concentration was 8 days after subcutaneous administration. Full PD-1 receptor occupancy was seen in all dose cohorts. Conclusions and Relevance Anti–PD-1 antibody PF-06801591 was tolerable and showed antitumor activity in a variety of tumor types across all dose levels of intravenous and subcutaneous administration. Monthly subcutaneous administration of PF-06801591 offers a convenient, effective alternative to currently available intravenously administered checkpoint inhibitors. Trial Registration ClinicalTrials.gov identifier:NCT02573259

Neurotrophic factors have been considered as potential therapeutics for peripheral neuropathies. Previously, we showed that neurotrophin-3 (NT-3) promotes nerve regeneration in TremblerJ (TrJ) mice and in sural nerves from patients with Charcot–Marie–Tooth 1A (CMT1A). The relatively short plasma half-life of NT-3 and other neurotrophins, however, pose a practical difficulty in their clinical application. Therapeutic agonist antibodies (AAb) targeting the neurotrophic receptors may circumvent this obstacle due to their high specificity and long half-life. Using morphological, electrophysiological studies and functional motor testing, we assessed the efficacy of monoclonal TrkC AAb and TrkB AAb in the TrJ mice. Treatments of these AAbs individually or in combination over 20 weeks increased compound muscle action potential (CMAP) amplitude, which correlated with improved grip strength, as compared to the PBS control group. Improvements in CMAP amplitude were most prominent with TrkC AAb treatment. In all treatment groups, distal to the crush site of the sciatic nerves exhibited a significantly greater number of myelinated fibers (MFs) indicating improved regenerative response to injury. In the contralateral intact sciatic nerves, the number of MFs as well as the myelin thickness was also increased significantly by the AAb treatments, suggesting that the hypomyelination/amyelination state of the peripheral nerves in TrJ improved. Therapeutic response to AAb combination was often, albeit not always, the most prominent, indicating a non-redundant effect of TrkB and TrkC AAbs. An early functional recovery and the correlative morphological changes of enhanced regeneration were seen with TrkC AAb treatment. These results provide evidence for potential therapeutic use of monoclonal agonist antibodies for neurotrophin receptors in CMT1A and other neuropathies.

The uncleaved, pro-form of nerve growth factor (proNGF) functions as a pro-apoptotic ligand for the p75 neurotrophin receptor (p75NTR). However, some reports have indicated that proneurotrophins bind and activate Trk receptors. In this study, we have examined proneurotrophin receptor binding and activation properties in an attempt to reconcile these findings. We show that proNGF readily binds p75NTR expressed in HEK293T cells but does not interact with TrkA expressed under similar circumstances. Importantly, proNGF activates TrkA tyrosine phosphorylation, induces Erk and Akt activation, and causes PC12 cell differentiation. We show that inhibiting endocytosis or furin activity reduced TrkA activation induced by proNGF but not that induced by mature NGF and that proNGF123, a mutant form of NGF lacking dibasic cleavage sites in the prodomain, does not induce TrkA phosphorylation in PC12 cells. Therefore, endocytosis and cleavage appear to be prerequisites for proNGF-induced TrkA activity. We also found that proBDNF induces activation of TrkB in cerebellar granule neurons and that proBDNF cleavage by furin and metalloproteases facilitates this effect. Taken together, these data indicate that under physiological conditions, proneurotrophins do not directly bind or activate Trk receptors. However, endocytosis and cleavage of proneurotrophins produce processed forms of neurotrophins that are capable of inducing Trk activation.

Macrophage stimulating protein (MSP) is a pleiotropic growth factor that signals via the Ron receptor tyrosine kinase. We report that Ron mRNA is expressed by NGF-dependent sensory and sympathetic neurons and that these neurons survive and grow with MSP at different stages of development. Whereas NGF-dependent sensory neurons become increasingly responsive to MSP with age,sympathetic neurons exhibit an early response to MSP that is lost by birth. MSP mRNA expression increases with age in sensory neuron targets and decreases in sympathetic targets. After the phase of naturally occurring neuronal death,significant numbers of NGF-dependent sensory neurons, but not sensory neurons,dependent on other neurotrophins, are lost in mice lacking a functional Ron receptor. These results show that MSP is a target-derived neurotrophic factor for subsets of sensory and sympathetic neurons at different times during their development.

Nerve growth factor (NGF) is indispensable during normal embryonic development and critical for the amplification of pain signals in adults. Intervention in NGF signaling holds promise for the alleviation of pain resulting from human diseases such as osteoarthritis, cancer and chronic lower back disorders. We developed a fast, high-fidelity method to convert a hybridoma-derived NGF-targeted mouse antibody into a clinical candidate. This method, termed Library Scanning Mutagenesis (LSM), resulted in the ultra-high affinity antibody tanezumab, a first-in-class anti-hyperalgesic specific for an NGF epitope. Functional and structural comparisons between tanezumab and the mouse 911 precursor antibody using neurotrophin-specific cell survival assays and X-ray crystal structures of both Fab-antigen complexes illustrated high fidelity retention of the NGF epitope. These results suggest the potential for wide applicability of the LSM method for optimization of well-characterized antibodies during humanization.

The sensory neurons of the nodose ganglion are the classic example of a population of peripheral nervous system neurons that do not require nerve growth factor (NGF) for survival during development but are dependent on other neurotrophins. We have re-examined this assertion by studying the development of the nodose ganglion of mice that have a null mutation in the NGF gene. Compared with wild-type embryos, the number of neurons undergoing apoptosis was elevated in NGF –/– mice, resulting in a significant reduction in the total number of neurons in the ganglion by the end of embryonic development. TrkA, the NGF receptor tyrosine kinase, was expressed in the nodose ganglion throughout development and there was a marked decrease in TrkA mRNA expression in the nodose ganglion of NGF –/– embryos. Although the in vitro survival of the majority of nodose neurons was promoted by brain-derived neurotrophic factor (BDNF), a minor proportion was supported by NGF in cultures established over a range of embryonic stages. These results clearly demonstrate that a subset of nodose ganglion neurons depends on NGF for survival during development. The finding that the expression of tyrosine hydroxylase (TH) mRNA was unaffected in the nodose ganglia of NGF-deficient embryos indicates that this NGF-dependent subset is distinct from the subset of catacholaminergic neurons in the nodose ganglion.

Glial cell line-derived neurotrophic factor (GDNF) is a distant member of the TGFbeta protein family that is essential for neuronal survival and renal morphogenesis. We show that mice who are deficient in the glycosyl-phosphatidyl inositol (GPI) -linked protein GFRalpha1 (GDNFRalpha) display deficits in the kidneys, the enteric nervous system, and spinal motor and sensory neurons that are strikingly similar to those of the GDNF- and Ret-deficient mice. GFRalpha1-deficient dopaminergic and nodose sensory ganglia neurons no longer respond to GDNF or to the structurally related protein neurturin (NTN) but can be rescued when exposed to GDNF or neurturin in the presence of soluble GFRalpha1. In contrast, GFRalpha1-deficient submandibular parasympathetic neurons retain normal response to these two factors. Taken together with the available genetic and biochemical data, these findings support the idea that GFRalpha1 and the transmembrane tyrosine kinase Ret are both necessary receptor components for GDNF in the developing kidney and nervous system, and that GDNF and neurturin can mediate some of their activities through a second receptor.

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a fatal autosomal recessive disorder seen in infants. It is characterized by lower motor neuron degeneration, progressive muscle paralysis and respiratory failure, for which no effective treatment exists. The phenotype of neuromuscular degeneration (nmd) mice closely resembles the human SMARD1. The identification of the mutated mouse gene in nmd mice ,I ghmbp2, led to the discovery of mutations of the homologous gene in humans with SMARD1. We have studied the nmd mouse model with in vivo electrophysiological techniques and evaluated the efficacy of Mab2256, a monoclonal antibody with agonist effect on the tyrosine kinase receptor C, trkC, on disease progression in nmd mice. Treatment with Mab2256 resulted in a significant but transient improvement of muscle strength in nmd mice, as well as normalization of the neuromuscular depression during highfrequency nerve stimulation. These results suggest the potential of using monoclonal agonist antibodies for neurotrophin receptors in lower motor neuron diseases such as SMARD1.

We have studied the ability of GDNF and neurturin to promote the in vitro survival of populations of embryonic chicken parasympathetic, sympathetic, and sensory neurons. We show that these neurons are more responsive to one or other of these factors at particular stages of development. Whereas the parasympathetic neurons are more sensitive to neurturin at late embryonic stages, sympathetic neurons are more sensitive to neurturin at early stages. In contrast, sensory neurons of the nodose ganglion are more sensitive to GDNF throughout embryonic development. Using competitive RT/PCR, we measured the levels of mRNAs encoding GDNF and neurturin receptors in purified neurons. All neurons expressed Ret mRNA, which encodes the common receptor tyrosine kinase for GDNF and neurturin. Neurons that were more sensitive to GDNF expressed higher levels of GFRalpha-1 mRNA than GFRalpha-2 mRNA and neurons that were more sensitive to neurturin expressed higher levels of GFRalpha-2 mRNA than GFRalpha-1 mRNA. These results show that populations of PNS neurons differ markedly in their responsiveness to GDNF and neurturin at certain stages of the development and suggest that these differences are governed in part by the relative levels of expression of members of the GFRalpha family of GPI-linked receptors.

To define the role of artemin in sympathetic neurone development, we have studied the effect of artemin on the generation, survival and growth of sympathetic neurones in low-density dissociated cultures of mouse cervical and thoracic paravertebral sympathetic ganglia at stages throughout embryonic and postnatal development. Artemin promoted the proliferation of sympathetic neuroblasts and increased the generation of new neurones in cultures established from E12 to E14 ganglia. Artemin also exerted a transient survival-promoting action on newly generated neurones during these early stages of development. Between E16 and P8, artemin exerted no effect on survival, but by P12, as sympathetic neurones begin to acquire neurotrophic factor independent survival, artemin once again enhanced survival, and by P20 it promoted survival as effectively as nerve growth factor (NGF). During this late period of development, artemin also enhanced the growth of neurites from cultured neurones more effectively than NGF. Confirming the physiological relevance of the mitogenic action of artemin on cultured neuroblasts, there was a marked reduction in the rate of neuroblast proliferation in the sympathetic ganglia of mice lacking the GFRα3 subunit of the artemin receptor. These results indicate that artemin exerts several distinct effects on the generation, survival and growth of sympathetic neurones at different stages of development.