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Purpose: Acquired RET fusions have been reported at resistance to treatment with EGFR inhibitors in EGFR-mutant non–small cell lung cancer (NSCLC); however, a multicenter cohort of patients with EGFR-mutant lung cancers treated with osimertinib and selpercatinib for RET fusion–mediated osimertinib resistance has not previously been published. Patients and Methods: Patients who received selpercatinib in combination with osimertinib on a prospective expanded access clinical trial (NCT03906331) and single-patient compassionate use programs across five countries were centrally analyzed. All patients had advanced EGFR-mutant NSCLC with a RET fusion detected from tissue or plasma following osimertinib therapy. Clinicopathologic and outcomes data were collected. Results: Fourteen patients with EGFR-mutant and RET fusion–positive lung cancers who experienced prior progression on osimertinib received osimertinib and selpercatinib. EGFR exon 19 deletions (±T790M, 86%) and non-KIF5B fusions (CCDC6-RET 50%, NCOA4-RET 36%) predominated. Osimertinib 80 mg daily and selpercatinib 80 mg twice daily were the most commonly administered dosages. The response rate, disease control rate, and median treatment duration were 50% [95% confidence interval (CI), 25%–75%, n = 12], 83% (95% CI, 55%–95%), and 7.9 months (range, 0.8–25+), respectively. Resistance was complex, involving EGFR on-target (EGFR C797S), RET on-target (RET G810S), and off-target (EML4–ALK/STRN–ALK, KRAS G12S, BRAF V600E) mechanisms; RET fusion loss; or polyclonal mechanisms. Conclusions: For patients with EGFR-mutant NSCLC with an acquired RET fusion as a mechanism of EGFR inhibitor resistance, the addition of selpercatinib to osimertinib was feasible and safe and offered clinical benefit, supporting the prospective evaluation of this combination.

Combination therapy dosing

Purpose:Acquired RET fusions have been reported at resistance to treatment with EGFR inhibitors in EGFR-mutant non–small cell lung cancer (NSCLC); however, a multicenter cohort of patients with EGFR-mutant lung cancers treated with osimertinib and selpercatinib for RET fusion–mediated osimertinib resistance has not previously been published.Patients and Methods:Patients who received selpercatinib in combination with osimertinib on a prospective expanded access clinical trial (NCT03906331) and single-patient compassionate use programs across five countries were centrally analyzed. All patients had advanced EGFR-mutant NSCLC with a RET fusion detected from tissue or plasma following osimertinib therapy. Clinicopathologic and outcomes data were collected.Results:Fourteen patients with EGFR-mutant and RET fusion–positive lung cancers who experienced prior progression on osimertinib received osimertinib and selpercatinib. EGFR exon 19 deletions (±T790M, 86%) and non-KIF5B fusions (CCDC6-RET 50%, NCOA4-RET 36%) predominated. Osimertinib 80 mg daily and selpercatinib 80 mg twice daily were the most commonly administered dosages. The response rate, disease control rate, and median treatment duration were 50% [95% confidence interval (CI), 25%–75%, n = 12], 83% (95% CI, 55%–95%), and 7.9 months (range, 0.8–25+), respectively. Resistance was complex, involving EGFR on-target (EGFR C797S), RET on-target (RET G810S), and off-target (EML4–ALK/STRN–ALK, KRAS G12S, BRAF V600E) mechanisms; RET fusion loss; or polyclonal mechanisms.Conclusions:For patients with EGFR-mutant NSCLC with an acquired RET fusion as a mechanism of EGFR inhibitor resistance, the addition of selpercatinib to osimertinib was feasible and safe and offered clinical benefit, supporting the prospective evaluation of this combination.

Patient Cohort Identification

Supplementary Figure Legends

Comparative mRNA expression of MET exons 2-3, 14, and 20-21 from 5 patients with MET exon 14 splicing variants. All tumor samples tested had significantly and markedly lower expression of exon 14 in keeping with the transcriptional effects of the splice site mutations.

Representative photomicrographs from 3 patient samples demonstrating tumor localization on the left (H&E staining) and MET protein expression by IHC on the right. High membranous MET protein expression by IHC is present in all samples (H-score = 300).

nanoString probe sequences for MET exons 3, 4, 14, 20, and 21.

Study selection flow diagram

EGFR-TKI resistance mechanisms by TMB tertile

Demographics by EGFR-mutant allele and smoking status

Full annotated cohort of EGFR-mutant lung cancer patients evaluated (n = 153)

pre-EGFR-TKI TMB by TP53 co-mutation and incidence of TP53 co-mutation by tertile (low/intermediate vs high)

Purpose:Tumor mutation burden (TMB) is a biomarker of response to immune checkpoint blockade (ICB). The impact of TMB on outcomes with targeted therapies has not been explored.Experimental Design:We identified all patients with metastatic EGFR exon19del or L858R-mutant lung cancers treated with first/second-generation EGFR tyrosine kinase inhibitors (TKIs) with pretreatment next-generation sequencing data (MSK-IMPACT assay). The effect of TMB on time-to-treatment discontinuation (TTD) and overall survival (OS) were evaluated in univariate and multivariate analyses. EGFR wild-type lung adenocarcinoma samples were used for comparison.Results:Among 153 patients with EGFR-mutant lung cancer, TMB was lower compared with EGFR wild-type (n = 1,849; median 3.77 vs. 6.12 mutations/Mb; P < 0.0001) with a broad range (0.82–17.9 mutations/Mb). Patients with EGFR-mutant lung cancer whose tumors had TMB in the high tertile had shorter TTD (HR, 0.46; P = 0.0008) and OS (HR, 0.40; P = 0.006) compared with patients with low/intermediate TMB. Evaluating by median TMB, there was significantly shorter TTD and OS for patients with higher TMB (TTD, P = 0.006; OS, P = 0.03). In multivariate analysis, TTD and OS remained significantly longer in the low/intermediate tertile compared with high TMB (HR = 0.57, P = 0.01; HR = 0.50, P = 0.02, respectively). In paired pretreatment and postprogression samples, TMB was increased at resistance (median 3.42 vs. 6.56 mutations/Mb; P = 0.008).Conclusions:TMB is negatively associated with clinical outcomes in metastatic patients with EGFR-mutant lung cancer treated with EGFR-TKI. This relationship contrasts with that seen in lung cancers treated with immunotherapy.See related commentary by Cheng and Oxnard, p. 899

Univariate and multivariate analysis of TTD and OS by median TMB

Up to 50% of patients with non-small cell lung cancer (NSCLC) develop brain metastasis (BM), yet the study of BM genomics has been limited by tissue access, incomplete clinical data, and a lack of comparison with paired extracranial specimens. Here we report a cohort of 233 patients with resected and sequenced (MSK-IMPACT) NSCLC BM and comprehensive clinical data. With matched samples (47 primary tumor, 42 extracranial metastatic), we showed CDKN2A/B deletions and cell cycle pathway alterations to be enriched in the BM samples. Meaningful clinico-genomic correlations were noted, namely EGFR alterations in leptomeningeal disease (LMD) and MYC amplifications in multifocal regional brain progression. Patients who developed early LMD frequently had uncommon, multiple, and persistently detectable EGFR driver mutations. The distinct mutational patterns identified in BM specimens compared to other tissue sites suggest specific biologic underpinnings of intracranial progression.

Background: The epidermal growth factor receptor (EGFR) is a potent oncogene commonly altered in many cancers, including glioblastoma (GBM) and non-small cell lung cancer (NSCLC). EGFR tyrosine kinase activity driven by common EGFR mutations can be inhibited by small molecules, however, resistance to available agents may be driven by mutations in the EGFR active kinase site or other regions. BDTX-1535 is an orally available, highly potent, selective, irreversible inhibitor of EGFR mutations, including extracellular variants and amplifications commonly expressed in GBM and inhibits the uncommon EGFR mutations found in NSCLC, including the C797S mutation acquired following 3rd generation EGFR inhibitor therapy. Preclinical data demonstrated the ability of BDTX-1535 to cross the blood-brain barrier and produce sustained inhibition of EGFR signaling. Preclinical studies suggest that BDTX-1535 has potential to be clinically active in suppressing tumor growth in patients with GBM and NSCLC with or without CNS metastases, including a potential survival benefit. Methods: BDTX-1535-101 (NCT05256290) is Phase 1, open-label, multicenter study to assess the safety, tolerability, PK, CNS penetrance, and preliminary antitumor activity of BDTX-1535 in recurrent GBM (rGBM) or locally advanced or metastatic NSCLC with or without CNS disease. The Monotherapy Dose Escalation portion will evaluate BDTX-1535 in patients with either rGBM expressing EGFR alterations or locally advanced/metastatic NSCLC harboring sensitizing EGFR mutations with or without CNS disease. Patients with rGBM must have previously received available standard therapy of surgical resection followed by chemoradiotherapy and/or temozolomide (TMZ). Eligible NSCLC patients must have EGFR mutated NSCLC that has progressed following standard of care EGFR inhibitor therapy. Once a provisional recommended Phase 2 dose (RP2D) has been established, BDTX-1535 monotherapy will be explored in the following Dose Expansion cohorts to further evaluate safety, PK, and preliminary assessment of efficacy: 1) rGBM with confirmed EGFR alterations, 2) NSCLC with uncommon EGFR mutations following EGFR inhibitor therapy; 3) NSCLC with acquired EGFR resistance mutation following a 3rd generation EGFR inhibitor in 1L setting. NSCLC patients may enroll with or without CNS metastases and must not be known to express excluded resistance mutations such as EGFR T790M or MET. BDTX-1535 will also be studied in combination with TMZ to assess safety, tolerability, and a recommended combination dose for the treatment of patients with rGBM harboring EGFR mutations or variants. Enrollment was initiated in 2022 and dose escalation is ongoing. Dose Expansion cohorts are expected to open in 2023. For additional information, please contact BDTX_1535_101_Study@bdtx.com Citation Format: Melissa Johnson, Jason Henry, Alex Spira, James Battiste, Iyad Alnahhas, Manmeet Ahluwalia, Minal Barve, Jeffrey Edenfield, DoHyun Nam, Sudharshan Eathiraj, Julio Hajdenberg, Sergey Yurasov, Helena Yu, Patrick Wen. A phase 1 study to assess BDTX-1535, an oral EGFR inhibitor, in patients with glioblastoma or non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT127.

Lineage plasticity is the ability for a cell to change its phenotypic state under evolutionary pressure. This process mediates acquired resistance to EGFR-targeted therapies in lung adenocarcinoma (LUAD), through transformation to small cell lung cancer (SCLC), an aggressive cancer type of neuroendocrine (NE) histology. This transformed SCLC has worse clinical outcomes than either its LUAD or de novo SCLC counterparts, with less than one-year overall survival following transformation. Classical SCLC itself can display plasticity through interconversion between classical, variant, and non-NE transcriptional subtypes, with non-classical subtypes displaying increased metastasis and chemoresistance. It is poorly understood what factors drive SCLC transformation or subtype switching. Prior studies poorly model intratumoral heterogeneity because they profile tumors in bulk, which only estimates the average phenotype. However, SCLC transformation often results in admixed LUAD/SCLC tumors. We sought to capture the full intratumoral heterogeneity of SCLC transformation and identify potential molecular determinants of plasticity by applying single-cell RNA sequencing (scRNA-seq) to 41 tumors and patient-derived xenografts from 22 patients with transformed or combined LUAD/NE histology, with matched targeted DNA sequencing and 17 de novo SCLC tumors, 10 LUAD tumors with concurrent EGFR/RB1/TP53 mutations, and 4 tumor-adjacent normal lung samples for comparison. Of 234,322 single transcriptomes assessed, we found 89,113 NE cancer cells and 18,197 LUAD cancer cells. We confirmed that NE and LUAD components within the same tumor shared clonal mutations and common ancestry. Compared to de novo, transformed SCLC harbored greater phenotypic diversity across patients (p < 1 × 10−10), driven largely by enrichment of variant and non-NE subtypes (p < 0.02), including NEUROD1, POU2F3, and YAP1-high subtypes, the latter of which was completely absent in de novo. Within each tumor, transformed SCLC displayed higher intratumoral subtype diversity than de novo SCLC (likelihood ratio p < 0.025). After adjusting for SCLC subtype, differential expression and pathway analysis demonstrated that transformed SCLC is a distinct phenotype from de novo and shares features of the ancestral clone that include residual EGFR and NSCLC gene signatures, as well as pathways in neuronal stemness, MYC targets, AKT/MTOR signaling, JAK/STAT inflammation, and chromatin remodeling. In sum, we find increased intratumoral phenotypic diversity in transformed SCLC, including variant and non-NE subtypes, that may explain worse clinical outcomes. We show that transformed SCLC is a distinct phenotype from de novo, marked by pathways that may offer new potential drug targets to constrain plasticity, with the goal of restoring original sensitivity to targeted therapies. Citation Format: Joseph Minhow Chan, Alvaro Quintanal-Villalonga, Amin Sabet, Parvathy Manoj, Ojasvi Chaudhary, Tianhao Xu, Ignas Masilionis, Jacklynn Egger, Noor Sohail, Jaeyoung Chun, Tal Nawy, Linas Mazutis, Triparna Sen, Ronan Chaligne, Helena Yu, Dana Pe'er, Charles Rudin. Single-cell transcriptomic profiling of SCLC transformation reveals increased intratumoral diversity of variant and non-neuroendocrine subtypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1167.

Background/Purpose: Osimertinib, a third-generation, irreversible, EGFR tyrosine kinase inhibitor (TKI), is the preferred 1L treatment for pts with EGFRm NSCLC. Unfortunately, most of these pts will eventually develop treatment resistance. ORCHARD is an ongoing Phase II platform study (NCT03944772) enrolling pts with EGFRm NSCLC, whose tumors progressed on 1L osimertinib, to a treatment group based on their tumor molecular profile. This exploratory analysis aimed to further understand the genomic landscape of resistance detected in tumor samples from pts with EGFRm NSCLC post-1L osimertinib, and to evaluate the concordance of resistance mechanisms identified in plasma and tissue. Methods: Pts enrolled on ORCHARD (with advanced EGFRm NSCLC) provided tissue/plasma samples after progression on 1L osimertinib. Samples were analyzed for resistance mechanisms and testing concordance using next generation sequencing (NGS) either centrally (tissue [Foundation Medicine]; plasma [Guardant Health]) or locally. Alterations were determined based on reported results from respective assay. Results: In total, 195 tissue samples (21 local and 174 central NGS) and 69 plasma samples (central NGS) were collected. The 174 central tissue samples were used for the genomic profiling: MET amplification occurred in 24% (42/174) of tumors; EGFR amplifications in 36% (62/174). Secondary EGFR mutations (C797X, L718X) and BRAF fusions were less common, 7% (13/174) and 5% (9/174), respectively, while other potentially actionable genomic alterations were rare: ERBB2 amplified/mutated (2%), ALK fusion (2%), RET fusions (1%), KRAS mutation (1%), BRAF V600E (1%).In the concordance analysis, 69 samples of matched tumor and plasma were used. Concordance was high between tissue and plasma for point mutations, particularly for sensitizing (64 samples; 89% concordance) and uncommon (G719X, L861X, S768I; 5 samples; 100% concordance) EGFR resistance mutations. The majority of EGFR (21/38 samples) and MET (16/30) amplifications were detected via tissue only. For BRAF, concordance was low: 4/5 BRAF fusions were found in tissue only, 1/5 in plasma only; 5/5 BRAF V600E mutations could be identified in plasma but only one of these was also identified in tissue. Conclusions: Genomic profiling of pts with disease progression after 1L osimertinib showed that the most common identifiable resistance mutations were consistent with previous studies, however MET, EGFR amplifications and BRAF fusions were identified at higher rates than expected. Tissue and plasma provided different but potentially complementary results for detecting mechanisms of resistance, with differing levels of concordance across the mutations; further study is required in this area. Further exploration of 1L osimertinib resistance is continuing in the ongoing ORCHARD study. Citation Format: Ryan J. Hartmaier, Aleksandra Markovets, Byoung Chul Cho, Adrianus J. de Langen, Sarah B. Goldberg, Jonathan Goldman, Xiuning Le, Isamu Okamoto, Jonathan W. Riess, Jan Cosaert, Helena Yu, Zofia Piotrowska. Tumor genomics in patients (pts) with advanced epidermal growth factor receptor mutant (EGFRm) non-small cell lung cancer (NSCLC) whose disease has progressed on first-line (1L) osimertinib therapy in the Phase II ORCHARD study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB078.

Background Leptomeningeal metastasis (LM) involves cerebrospinal fluid (CSF) seeding of tumor cells. Proton craniospinal irradiation (pCSI) is potentially effective for solid tumor LM. We evaluated whether circulating tumor cells (CTCs) in the CSF (CTCCSF), blood (CTCblood), and neuroimaging correlate with outcomes after pCSI for LM. Methods We describe a single-institution consecutive case series of 58 patients treated with pCSI for LM. Pre-pCSI CTCs, the change in CTC post-pCSI (Δ CTC), and MRIs were examined. Central nervous system progression-free survival (CNS-PFS) and overall survival (OS) from pCSI were determined using Kaplan Meier analysis, Cox proportional-hazards regression, time-dependent ROC analysis, and joint modeling of time-varying effects and survival outcomes. Results The median CNS-PFS and OS were 6 months (IQR: 4–9) and 8 months (IQR: 5–13), respectively. Pre-pCSI CTCCSF < 53/3mL was associated with improved CNS-PFS (12.0 vs 6.0 months, P < .01). Parenchymal brain metastases (n = 34, 59%) on pre-pCSI MRI showed worse OS (7.0 vs 13 months, P = .01). Through joint modeling, CTCCSF was significantly prognostic of CNS-PFS (P < .01) and OS (P < .01). A Δ CTC-CSF≥37 cells/3mL, the median Δ CTC-CSF at nadir, showed improved CNS-PFS (8.0 vs 5.0 months, P = .02) and further stratified patients into favorable and unfavorable subgroups (CNS-PFS 8.0 vs 4.0 months, P < .01). No associations with CTCblood were found. Conclusion We found the best survival observed in patients with low pre-pCSI CTCCSF and intermediate outcomes for patients with high pre-pCSI CTCCSF but large Δ CTC-CSF. These results favor additional studies incorporating pCSI and CTCCSF measurement earlier in the LM treatment paradigm.

Management of refractory pain in pediatric sickle cell disease (SCD) and oncology is reliant on opioids though high opioid dosing increases side effects and tachyphylaxis. We introduced low-dose ketamine infusion (LDKI) to our inpatient unit to determine if LDKI was tolerable. We subsequently hypothesized that LDKI would improve pain scores. We reviewed inpatients from LDKI initiation in March 2014 through October 2017, with the day before LDKI initiation compared with the day of LDKI initiation and 2 subsequent days. For patients with SCD, the LDKI admission was compared with up to 3 admissions in the prior year for a vaso-occlusive event. Nineteen patients (12 oncology, 7 SCD) with a median age of 14.6 years received LDKI for a median of 6 days at a median initial dose of 0.06 mg/kg/h (1.1 µg/kg/min). There was no change in pain scores or opioid utilization when comparing the day before LDKI initiation with subsequent days. No patient discontinued LDKI because of intolerability. For patients with SCD, there was a median 32% reduction in cumulative pain scores when comparing the LDKI admission with prior admissions. LDKI is well tolerated for refractory pediatric cancer-related and sickle cell-related pain.

Objective To determine factors associated with post-tracheotomy hospital readmission within 30 days of discharge. Methods Children 18 years and younger who underwent tracheotomy at Children's Hospital Los Angeles (CHLA) between 1/1/2005 and 12/31/2013 with at least 30 days of follow-up at CHLA were identified through ICD-9 procedure codes. Patient characteristics and covariates were obtained by linking manual chart review and administrative data. We used multivariate logistic regression to identify the independent association between risk factors and the primary outcome of 30-day all-cause same-hospital readmission. Results Of the 273 patients included, the median age at admission was 6 months [interquartile range (IQR): 1–51 months]. Among this primarily male (60.8%) and Hispanic (66.3%) cohort with a high proportion of discharge on positive pressure ventilation (47.1%), the 30-day readmission rate was 22% (n = 60). Of the readmissions, 92% (n = 55) were unplanned and 64% (n = 35) were associated with acute respiratory illnesses. Multivariate regression analysis demonstrated that, among patients ≤12 months, discharge on positive pressure ventilation [adjusted odds ratio (aOR) = 2.88, 95% confidence interval (CI) = 1.19–6.97] was associated with increased odds of readmission, while gastrostomy tube placement during the tracheotomy hospitalization (aOR = 0.42, 95% CI = 0.19–0.96) and prematurity (aOR = 0.35, 95% CI = 0.15–0.83) were associated with decreased odds of readmission. In patients >1 year of age, increased length of hospitalization (aOR = 1.01 per hospital day, 95% CI = 1–1.02) and presence of comorbid malignancy (aOR = 6.03, 95% CI = 1.25–29.16) were associated with increased odds of readmission. Conclusions Over one-fifth of children undergoing tracheotomy had an unplanned hospital readmission within 30 days after discharge. Because the majority of readmissions were unplanned and due to acute respiratory illnesses, future research should investigate how discharge procedures and improved care coordination may lower readmission rates in high-risk patients (e.g., patients discharged on positive pressure ventilation).

EGFR is frequently mutated in non-small-cell lung carcinomas (NSCLCs). Clinically available tyrosine kinase inhibitors (TKIs) are effective in treating EGFR-mutant NSCLC. In this case series, we present five patients with TKI-treated EGFR-mutated NSCLC who developed leptomeningeal disease (LMD) lacking characteristic imaging findings. All five patients received TKIs prior to development of cytology-confirmed LMD. Clinical signs of LMD preceded radiographic evidence by 2–12 months. T790M, the most common resistance mutation to first-generation EGFR inhibitors, was identified in four cases. These cases illustrate that in patients with EGFR-mutant NSCLC, TKIs may effectively control LMD, creating a lag between onset of symptoms and observation of radiographic findings.

Leptin receptor (LepRb) signaling pathway in the hypothalamus of the forebrain controls food intake and energy expenditure in response to an altered energy state. Defects in the LepRb signaling pathway can result in leptin-resistance and obesity. Leucine zipper transcription factor like 1 (Lztfl1)/BBS17 is a member of the Bardet–Biedl syndrome (BBS) gene family. Human BBS patients have a wide range of pathologies including obesity. The cellular and molecular mechanisms underlying Lztfl1-regulated obesity are unknown. Here, we generated Lztfl1f/f mouse model in which Lztfl1 can be deleted globally and in tissue-specific manner. Global Lztfl1 deficiency resulted in pleiotropic phenotypes including obesity. Lztfl1−/− mice are hyperphagic and showed similar energy expenditure as WT littermates. The obese phenotype of Lztfl1−/− mice is caused by the loss of Lztfl1 in the brain but not in the adipocytes. Lztfl1−/− mice are leptin-resistant. Inactivation of Lztfl1 abolished phosphorylation of Stat3 in the LepRb signaling pathway in the hypothalamus upon leptin stimulation. Deletion of Lztfl1 had no effect on LepRb membrane localization. Furthermore, we observed that Lztfl1−/− mouse embryonic fibroblasts (MEFs) have significantly longer cilia than WT MEFs. We identified several proteins that potentially interact with Lztfl1. As these proteins are known to be involved in regulation of actin/cytoskeleton dynamics, we suggest that Lztfl1 may regulate leptin signaling and ciliary structure via these proteins. Our study identified Lztfl1 as a novel player in the LepRb signaling pathway in the hypothalamus that controls energy homeostasis.

The EGFR T790M mutation is the most common cause of resistance in pts receiving a first or second-generation EGFR-TKI for EGFRm NSCLC. Other resistance mechanisms include upregulation of the RAS/RAF/MEK/ERK signaling pathway. The Phase Ib TATTON study (NCT02143466) assessed osimertinib in combination with novel therapeutics including the oral, potent and selective MEK1/2 inhibitor, selumetinib (AZD6244, ARRY-142886). Here we present data from the dose-finding (Part A) and dose expansion (Part B) portions of this study. Adults with advanced EGFRm NSCLC and disease progression on prior EGFR-TKI, including third-generation agents, were eligible regardless of T790M or KRAS status. In Part A, pts received osimertinib 80 mg QD plus intermittent or continuous selumetinib. Asian pts received continuous selumetinib 25/50 mg BID, while other pts received continuous selumetinib 50/75 mg BID, or intermittent selumetinib 75 mg BID 4 days on/3 days off (4/3), or on days 1 and 4 of each week of treatment. In Part B, pts received osimertinib plus intermittent selumetinib 75 mg BID 4/3. Primary objectives were safety, tolerability and preliminary efficacy (objective response rate [ORR]). Secondary objectives included duration of response (DoR) and pharmacokinetics (PK). At data cut-off (Feb 2018), 36 and 47 pts received treatment in Parts A and B, respectively. In Part A, most pts were white (18, 50%) or Asian (17, 47%), and 26 (72%) had a baseline exon 19 deletion. In Part B, 44 (94%) pts were Asian, and 30 (64%) had a baseline exon 19 deletion. The most common treatment-related adverse events (TRAEs) in Part A were diarrhea (27, 75%), nausea (14, 39%) and fatigue (12, 33%). Six pts had dose-limiting toxicities (DLTs) with continuous selumetinib (all Grade 3): ALT and AST increase (50 mg); diarrhea, asthenia and dizziness (50 mg); diarrhea (n=2, 75 mg); diarrhea and nausea (75 mg); and pneumonitis (75 mg). No DLTs were reported with intermittent dosing, so the selumetinib 4/3 schedule was selected for Part B. The most common TRAEs in Part B were diarrhea (38, 81%), stomatitis (15, 32%), and paronychia (14, 30%). In Part A, 15 (42%) pts had confirmed partial response (PR); 14 (39%) had stable disease at 6 weeks (SD); 3 (8%) had progressive disease (PD); 2 (6%) died; and 2 (6%) were not evaluable (NE). Median DoR was 16.6 months; 77% remained in response at 12 months. In Part B, 16 (34%) pts had confirmed PR; 16 (34%) had SD; 11 (23%) had PD; 2 (4%) died; and 2 (4%) were NE. Median DoR was 9.1 months; 31% remained in response at 12 months. Osimertinib and selumetinib PK parameters were similar to those previously observed with monotherapy. Osimertinib plus intermittent selumetinib had an acceptable safety profile and demonstrated preliminary anti-tumor activity in pts with disease progression on a prior EGFR-TKI. Responses were durable and this combination warrants further investigation. Citation Format: Suresh S. Ramalingam, Hideo Saka, Myung-Ju Ahn, Helena Yu, Helena Yu, Leora Horn, Toyoaki Hida, Mireille Cantarini, Remy Verheijen, Jonathan Wessen, Geoffrey Oxnard, Yuichiro Ohe. Osimertinib plus selumetinib for patients (pts) with EGFR-mutant (EGFRm) NSCLC following disease progression on an EGFR-TKI: Results from the Phase Ib TATTON study [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 CT034.

Although many connexin46 (Cx46) mutants have been linked to inherited human cataracts, there are no adequate animal models for their study. The current experiments were designed to characterize the consequences of expression of one such mutant, Cx46fs380, in the mouse lens.Mice expressing Cx46fs380 were generated by a knockin strategy. Levels and distribution of specific proteins were analyzed by immunoblotting and immunofluorescence.Dark-field microscopy revealed that lenses of young heterozygous and homozygous Cx46fs380 mice did not have opacities, but they developed anterior nuclear cataracts that became more severe with age. Immunofluorescence and immunoblotting showed that Cx46 was severely reduced in both heterozygous and homozygous Cx46fs380 lenses at 1 month of age, whereas immunoreactive connexin50 (Cx50) was moderately decreased. The reduction in Cx50 became more severe in older lenses. The solubilities of crystallins from young wild-type and fs380 mice were similar, but older fs380 lenses exhibited abnormalities of abundance, solubility, and modification of some crystallins.Major decreases in connexin levels precede the development of cataracts. These mice represent a useful model for elucidation of the progression of lens abnormalities during cataractogenesis especially as caused by a mutant connexin.

Growth at temperatures of >60°C and utilization of polysaccharides have not been reported previously in members of the genus Spirochaeta. Two obligately anaerobic, extremely thermophilic (optimum temperature, 65°C) spirochetes were isolated from geographically distant thermal sites. These two isolates have chemoorganotrophic fermentative metabolism and grow on a variety of mono-, di-, and polysaccharides, including cellulose. The differences in pH and NaCl concentration optima between these organisms reflect the prevailing conditions at the sites from which they were isolated. DNA-DNA hybridization showed that the two strains exhibit a level of homology of 87%. On the basis of their morphological characteristics, their high level of homology with each other, and their extremely thermophilic and polysaccharolytic nature, we propose that these organisms should be included in the genus Spirochaeta as a new species, Spirochaeta thermophila; the type strain of this species is strain Z-1203 (= DSM 6578).

PURPOSE Substitutions of aspartate-47 (D47) of Connexin50 (Cx50) have been linked to autosomal dominant congenital cataracts in several human pedigrees. To elucidate the lens abnormalities caused by a substitution at this position, we studied No2 mice, which carry the Cx50D47A mutation and parallel the human pathology. METHODS Lenses from mice of different ages (neonatal to 4 months) were examined by dark-field and immunofluorescence microscopy. Protein levels were determined by immunoblotting using primary antibodies directed against connexins, other membrane proteins, crystallins, and proteins residing in different organelles. RESULTS Lenses of both heterozygous and homozygous Cx50D47A mice had cataracts and were smaller than those of wild-type littermates. Levels of Cx50 were severely reduced in mutant animals as compared with those in wild-type mice (