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Background: MET mutations occur in 3-4% of advanced non-small cell lung cancer (aNSCLC), correlating with poor survival. Despite known sensitivity of MET mutated (METmut) aNSCLC to c-MET-inhibition, no approved therapies existed until 2022., Methods: In the Drug Rediscovery Protocol (NCT0295234), patients with an actionable molecular profile are treated with off-label registered drugs. Both treated and untreated patients with aNSCLC harboring MET exon 14 skipping (METex14) or other METmuts received crizotinib 250 mg BID until disease progression or intolerable toxicity. Primary endpoints were clinical benefit (CB: RECIST v1.1 confirmed partial response (PR), complete response (CR) or stable disease (SD) ≥16 weeks) and safety. Patients were enrolled using a Simon-like two-stage design, with eight patients in stage 1 and if ≥1/8 patients had CB, 24 patients in stage 2. Whole genome and RNA-sequencing were performed on baseline biopsies., Results: Between 09/2018 and 10/2022, 30 patients started treatment, and 24 were response-evaluable after completing ≥1 full treatment cycle. Two patients (8.3%) achieved CR, thirteen (54.2%) PR and two (8.3%) SD. The CB-rate was 70.8% (95%CI 48.9-87.4) and the objective response rate was 62.5% (95%CI 40.6-81.2). After 21.2 months median follow-up, median duration of response, progression-free and overall survival were 9.3 (95%CI 6.5-NA), 10.2 (95%CI 6.0-20.1) and 13.0 months (95%CI 9.0-NA), respectively. Twenty-three treatment-related grade ≥3 adverse events occurred in 12/30 patients (40%), causing treatment-discontinuation in three (10%). One patient (achieving CR) had a tyrosine kinase domain mutation (p.H1094Y), all other patients had METex14., Conclusions: Crizotinib is a valuable treatment option in METmut aNSCLC.

Purpose: The treatment efficacy of nivolumab was evaluated in patients with advanced, treatment-refractory solid mismatch repair deficiency/microsatellite-instable (dMMR/MSI) tumors, and in-depth biomarker analyses were performed to inform precision immunotherapy approaches., Patients and Methods: Patients with dMMR/MSI tumors who exhausted standard-of-care treatment options were enrolled in the Drug Rediscovery Protocol, a pan-cancer clinical trial that treats patients with cancer based on their tumor molecular profile with off-label anticancer drugs (NCT02925234). Patients received nivolumab (four cycles of 240 mg every 2 weeks, thereafter 480 mg every 4 weeks). The primary endpoint was clinical benefit (CB: objective response or stable disease ≥16 weeks). Whole-genome sequencing and RNA sequencing were performed on pretreatment tumor biopsies., Results: A total of 130 evaluable patients were enrolled with 16 different cancer types. CB was observed in 62% [95% confidence interval (CI), 53-70], with an objective response in 45% (95% CI, 36-54). After a median follow-up of 14.5 months (95% CI, 13-19), the median progression-free survival was 18 months (95% CI, 9-not reached), and the median overall survival was not reached. Whereas CB was not, or only weakly, associated with markers of adaptive immune cell infiltration, CB was strongly associated with expression of a broad set of innate immune receptors/ligands. This clearly contrasted findings in melanoma, in which markers of adaptive immunity dominated the biomarker landscape., Conclusions: Nivolumab proved highly effective in advanced dMMR/MSI tumors. Expression of key innate immune receptors/ligands was the main predictor of a good treatment outcome, contrasting findings in melanoma and strengthening the rationale for tumor type-specific biomarkers for guiding immunotherapy., (©2024 American Association for Cancer Research.)

Purpose: To evaluate the efficacy of pembrolizumab across multiple cancer types harboring different levels of whole-genome sequencing-based tumor mutational load (TML; total of nonsynonymous mutations across the genome) in patients included in the Drug Rediscovery Protocol (NCT02925234)., Patients and Methods: Patients with solid, treatment-refractory, microsatellite-stable tumors were enrolled in cohort A: breast cancer cohort harboring a TML of 140 to 290, cohort B: tumor-agnostic cohort harboring a TML of 140 to 290, and cohort C: tumor-agnostic cohort harboring a TML >290. Patients received pembrolizumab 200 mg every 3 weeks. The primary endpoint was clinical benefit [CB; objective response or stable disease (SD) ≥16 weeks]. Pretreatment tumor biopsies were obtained for whole-genome sequencing and RNA sequencing., Results: Seventy-two evaluable patients with 26 different histotypes were enrolled. The CB rate was 13% in cohort A [3/24 with partial response (PR)], 21% in cohort B (3/24 with SD; 2/24 with PR), and 42% in cohort C (4/24 with SD; 6/24 with PR). In cohort C, neoantigen burden estimates and expression of inflammation and innate immune biomarkers were significantly associated with CB. Similar associations were not identified in cohorts A and B. In cohort A, CB was significantly associated with mutations in the chromatin remodeling gene PBRM1, whereas in cohort B, CB was significantly associated with expression of MICA/MICB and butyrophilins. CB and clonal TML were not significantly associated., Conclusions: Although pembrolizumab lacked activity in cohort A, cohorts B and C met the study's primary endpoint. Further research is warranted to refine the selection of patients with tumors harboring lower TMLs and may benefit from a focus on innate immunity. See related commentary by Hsu and Yen, p. 3652., (©2024 American Association for Cancer Research.)

Purpose: Although eligibility criteria are essential in trial design, overly restrictive criteria contribute to low accrual and limited generalizability. To enhance trial inclusivity, there has been growing interest in broadening eligibility criteria, especially for patients with advanced or treatment-refractory disease. Yet, the impact on patient safety remains uncertain. In the Drug Rediscovery Protocol (DRUP), protocol exceptions are frequently requested and occasionally granted. Here we describe the impact of these waivers on treatment safety and efficacy., Experimental Design: DRUP is a multicenter, nonrandomized clinical basket trial treating patients with therapy-refractory cancer with molecularly targeted and immunotherapies outside their registered indications (NCT02925234). Here, all granted waivers were revised, analyzed in terms of safety and efficacy outcome, and comparedwithoutcomes of includedpatientswho didnot receive awaiver., Results: Between September 1, 2016, and September 1, 2021, protocol waivers were granted for 82 patients (8%) of 1,019 included patients in DRUP. Most waivers (45%) were granted for general- or drug-related eligibility criteria; other categories were out-of-window testing, treatment, and testing exceptions. Serious adverse event rate was similar between patients who received a waiver (pW) and patients who did not (pNW): 39% vs. 41%, respectively (P = 0.81). The clinical benefit (either objective response or stable disease ≥ 16 weeks) rate of pW was 40% versus 33% in pNW (P = 0.43)., Conclusions: Safety and clinical benefit were preserved in patients for whom a waiver was granted. These data support a more personalized approach in assessing eligibility criteria, especially in trials with widely used and approved drugs accruing patients without other treatment options. See related commentary by Waqar and Govindan, p. 3655., (©2024 American Association for Cancer Research.)

In the Drug Rediscovery Protocol (DRUP), patients with cancer are treated based on their tumor molecular profile with approved targeted and immunotherapies outside the labeled indication. Importantly, patients undergo a tumor biopsy for whole-genome sequencing (WGS) which allows for a WGS-based evaluation of routine diagnostics. Notably, we observed that not all biopsies of patients with dMMR/MSI-positive tumors as determined by routine diagnostics were classified as microsatellite-unstable by subsequent WGS. Therefore, we aimed to evaluate the discordance rate between routine dMMR/MSI diagnostics and WGS and to further characterize discordant cases. We assessed patients enrolled in DRUP with dMMR/MSI-positive tumors identified by routine diagnostics, who were treated with immune checkpoint blockade (ICB) and for whom WGS data were available. Patient and tumor characteristics, study treatment outcomes, and material from routine care were retrieved from the patient medical records and via Palga (the Dutch Pathology Registry), and were compared with WGS results. Initially, discordance between routine dMMR/MSI diagnostics and WGS was observed in 13 patients (13/121; 11%). The majority of these patients did not benefit from ICB (11/13; 85%). After further characterization, we found that in six patients (5%) discordance was caused by dMMR tumors that did not harbor an MSI molecular phenotype by WGS. In six patients (5%), discordance was false due to the presence of multiple primary tumors (n = 3, 2%) and misdiagnosis of dMMR status by immunohistochemistry (n = 3, 2%). In one patient (1%), the exact underlying cause of discordance could not be identified. Thus, in this group of patients limited to those initially diagnosed with dMMR/MSI tumors by current routine diagnostics, the true assay-based discordance rate between routine dMMR/MSI-positive diagnostics and WGS was 5%. To prevent inappropriate ICB treatment, clinicians and pathologists should be aware of the risk of multiple primary tumors and the limitations of different tests. © 2024 The Pathological Society of Great Britain and Ireland., (© 2024 The Pathological Society of Great Britain and Ireland.)

Background and Purpose: The Drug Rediscovery Protocol (DRUP) is a Dutch, pan-cancer, nonrandomized clinical trial that aims to investigate the efficacy and safety of targeted and immunotherapies outside their registered indication in patients with advanced or metastatic cancer., Patients: Patients with advanced or metastatic cancer are eligible when there are no standard of care treatment options left and the tumor possesses a molecular genomic variant for which commercially available anticancer treatment is accessible off-label in DRUP. Clinical benefit is the study's primary endpoint, characterized by a confirmed objective response or stable disease after at least 16 weeks of treatment., Results: More than 2,500 patients have undergone evaluation, of which over 1,500 have started treatment in DRUP. The overall clinical benefit rate (CBR) remains 33%. The nivolumab cohort for patients with microsatellite instable metastatic tumors proved highly successful with a CBR of 63%, while palbociclib or ribociclib in patients with tumors harboring CDK4/6 pathway alterations showed limited efficacy, with a CBR of 15%. The formation of two European initiatives (PCM4EU and PRIME-ROSE) strives to accelerate implementation and enhance data collection to broaden equitable access to anticancer treatments and gather more evidence., Conclusion: DRUP persists in improving patients access to off-label targeted or immunotherapy in the Netherlands and beyond. The expansion of DRUP-like clinical trials across Europe provides countless opportunities for broadening the horizon of precision oncology.

Background: The prognosis of malignant primary high-grade brain tumors, predominantly glioblastomas, is poor despite intensive multimodality treatment options. In more than 50% of patients with glioblastomas, potentially targetable mutations are present, including rearrangements, altered splicing, and/or focal amplifications of epidermal growth factor receptor (EGFR) by signaling through the RAF/RAS pathway. We studied whether treatment with the clinically available anti-EGFR monoclonal antibody panitumumab provides clinical benefit for patients with RAF/RAS-wild-type (wt) glioblastomas in the Drug Rediscovery Protocol (DRUP)., Methods: Patients with progression of treatment refractory RAF/RASwt glioblastoma were included for treatment with panitumumab in DRUP when measurable according to RANO criteria. The primary endpoints of this study are clinical benefit (CB: defined as confirmed objective response [OR] or stable disease [SD] ≥ 16 weeks) and safety. Patients were enrolled using a Simon-like 2-stage model, with 8 patients in stage 1 and up to 24 patients in stage 2 if at least 1 in 8 patients had CB in stage 1., Results: Between 03-2018 and 02-2022, 24 evaluable patients were treated. CB was observed in 5 patients (21%), including 2 patients with partial response (8.3%) and 3 patients with SD ≥ 16 weeks (12.5%). After median follow-up of 15 months, median progression-free survival and overall survival were 1.7 months (95% CI 1.6-2.1 months) and 4.5 months (95% CI 2.9-8.6 months), respectively. No unexpected toxicities were observed., Conclusions: Panitumumab treatment provides limited CB in patients with recurrent RAF/RASwt glioblastoma precluding further development of this therapeutic strategy., (© The Author(s) 2023. Published by Oxford University Press.)

Background: In 2-5% of patients with colorectal cancer (CRC), human epidermal growth factor 2 (HER2) is amplified or overexpressed. Despite prior evidence that anti-HER2 therapy confers clinical benefit (CB) in one-third of these patients, it is not approved for this indication in Europe. In the Drug Rediscovery Protocol (DRUP), patients are treated with off-label drugs based on their molecular profile. Here, we present the results of the cohort 'trastuzumab/pertuzumab for treatment-refractory patients with RAS/BRAF-wild-type HER2amplified metastatic CRC (HER2+mCRC)'., Methods: Patients with progressive treatment-refractory RAS/BRAF-wild-type HER2+mCRC with measurable disease were included for trastuzumab plus pertuzumab treatment. Primary endpoints of DRUP are CB (defined as confirmed objective response (OR) or stable disease (SD) ≥ 16 weeks) and safety. Patients were enrolled using a Simon-like 2-stage model, with 8 patients in stage 1 and 24 patients in stage 2 if at least 1/8 patients had CB. To identify biomarkers for response, whole genome sequencing (WGS) was performed on pre-treatment biopsies., Results: CB was observed in 11/24 evaluable patients (46%) with HER2+mCRC, seven patients achieved an OR (29%). Median duration of response was 8.4 months. Patients had undergone a median of 3 prior treatment lines. Median progression-free survival and overall survival were 4.3 months (95% CI 1.9-10.3) and 8.2 months (95% CI 7.2-14.7), respectively. No unexpected toxicities were observed. WGS provided potential explanations for resistance in 3/10 patients without CB, for whom WGS was available., Conclusions: The results of this study confirm a clinically significant benefit of trastuzumab plus pertuzumab treatment in patients with HER2+mCRC., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Derk-Jan A. de Groot received funding for research grants from Siemens and Hoffman-La Roche. All outside the submitted work and all money had been received by the UMCG. Jeanine M.L. Roodhardt is a member of Advisory boards from Bayer, BMS, Merck-Serono, Pierre Fabre, Servier, GSK and Amgen (all paid to institution), received research funding from BMS, Pierre Fabre, Servier, Cleara, Xilis, DoMore diagnostics and HUB organoids B.V. (all paid to institution) and is a Board Member of Foundation Hubrecht Oragnoid Biobank. Liselot Valkenburg-van Iersel reported consulting fees from Sevier, Amgen and Pierre Fabre. Emile E. Voest is founder and current member of the supervisory board of the Hartwig Medical Foundation, independent non-executive director of Sanofi, co-founder of Mosaic Therapeutics, and a board member and founder of the Center for Personalized Cancer Treatment. He has received clinical study grants from Amgen, AstraZenica, BI, BMS, Clovis, Eli Lilly, GSK, Ipsen, MSD, Novartis, Pfizer, Roche and Sanofi, all paid to the Netherlands Cancer Institute. The other authors declare no conflicts of interests., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Microbial communities are resident to multiple niches of the human body and are important modulators of the host immune system and responses to anticancer therapies. Recent studies have shown that complex microbial communities are present within primary tumors. To investigate the presence and relevance of the microbiome in metastases, we integrated mapping and assembly-based metagenomics, genomics, transcriptomics, and clinical data of 4,160 metastatic tumor biopsies. We identified organ-specific tropisms of microbes, enrichments of anaerobic bacteria in hypoxic tumors, associations between microbial diversity and tumor-infiltrating neutrophils, and the association of Fusobacterium with resistance to immune checkpoint blockade (ICB) in lung cancer. Furthermore, longitudinal tumor sampling revealed temporal evolution of the microbial communities and identified bacteria depleted upon ICB. Together, we generated a pan-cancer resource of the metastatic tumor microbiome that may contribute to advancing treatment strategies., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The DRUG Access Protocol provides patients with cancer access to registered anti-cancer drugs that are awaiting reimbursement in the Netherlands and simultaneously collects prospective real-world data (RWD). Here, we present RWD from PD-1 blocker cemiplimab in patients with locally advanced or metastatic cutaneous squamous cell carcinoma (laCSCC; mCSCC)., Methods: Patients with laCSCC or mCSCC received cemiplimab 350 mg fixed dose every three weeks. Primary endpoints were objective clinical benefit rate (CBR), defined as objective response (OR) or stable disease (SD) at 16 weeks, physician-assessed CBR, defined as clinician's documentation of improved disease or SD based on evaluation of all available clinical parameters at 16 weeks, objective response rate (ORR), and safety, defined as grade ≥ 3 treatment related adverse events (TRAEs) occurring up to 30 days after last drug administration. Secondary endpoints included duration of response (DoR), progression-free survival (PFS), and overall survival (OS)., Findings: Between February 2021 and December 2022, 151 patients started treatment. Objective and physician-assessed CBR were 54.3% (95% CI, 46.0-62.4) and 59.6% (95% CI, 51.3-67.5), respectively. ORR was 35.1% (95% CI, 27.5-43.3). After a median follow-up of 15.2 months, median DoR was not reached. Median PFS and OS were 12.2 (95% CI, 7.0-not reached) and 24.2 months (95% CI, 18.8-not reached), respectively. Sixty-eight TRAEs occurred in 29.8% of patients. Most commonly reported TRAE was a kidney transplant rejection (9.5%)., Interpretation: Cemiplimab proved highly effective and safe in this real-world cohort of patients with laCSCC or mCSCC, confirming its therapeutic value in the treatment of advanced CSCC in daily clinical practice., Funding: The DRUG Access Protocol is supported by all participating pharmaceutical companies: Bayer, Janssen, Lilly, Merck, Novartis, Roche, and Sanofi., Competing Interests: John B.A.G. Haanen reports research grants to the institution from Asher Bio, Amgen, BioNTech, Bristol Myers Squibb, Novartis, and Sastra Cell Therapy, consultation fees to the institution from Achilles Tx, AstraZeneca, BioNTech, Bristol Myers Squibb, CureVac, Eisai, GlaxoSmithKline, Imcyse, Immunocore, Instil Bio, Iovance Bio, Merck, Merck Sharp & Dohme, Neogene Tx, Novartis, Obsidian Tx, Roche, Sanofi, Sastra Cell Therapy, Third Rock Ventures, and T-Knife, and stock options from Neogene Tx and Sastra Cell Therapy. Mathilde Jalving received compensation to the institution for advisory roles for Pierre Fabre, Merck, and Novartis. Lot A. Devriese received compensation to the institution for advisory roles and education for Bristol Myers Squibb, Merck Sharp & Dohme, and Incyte. Astrid A.M. van der Veldt received compensation to the institution for advisory roles for Bristol Myers Squibb, Merck Sharp & Dohme, Eisai, Ipsen, Novartis, Pierre Fabre, Pfizer, Roche, and Sanofi. Maureen J.B. Aarts reports research grants to the institution from Merck-Pfizer and consultation fees to the institution from being on the advisory board from Amgen, Bristol Myers Squibb, Novartis, Merck Sharp & Dohme, Merck-Pfizer, Pierre Fabre, Sanofi, Astellas, and Bayer. Carla M.L. van Herpen reports research grants to the institution from Astra Zeneca, Bayer, Bristol Myers Squibb, Elevar, Ipsen, Merck Sharp & Dohme, Merck, Novartis, and Sanofi, payments for lectures to the institution from ICCR, NIFU, RIVM, Roije Congressen, Nederlands Paramedisch Instituut, Elevar, and Uitgeverij Jaap, and payments to the institution for participating on an advisory board to the institution from Elevar. Mariette Labots received compensation to the institution for education for Bristol Myers Squibb and Janssen. Sahar Barjesteh van Waalwijk van Doorn-Khosrovani reports the PRIME-ROSE—A European precision cancer medicine trial network and implementation initiative funded by the EU Cancer Mission; grant no. 101104269 paid to the Leiden University Medical Center and travel expenses for attending meetings at the Nordic Precision Medicine Forum and Center for Innovation in Regulatory Science. Egbert F. Smit reports compensation to the institution for advisory roles at AstraZeneca, Bristol Myers Squibb, Boehringer Ingelheim, Daiichi Sankyo, Eli Lilly, Janssen, Merck Sharp & Dohme, Roche, Sanofi, and Takeda, personal compensation for education from Boehringer Ingelheim and Daiichi Sankyo, and compensation to the institution for participation in the data safety monitoring board of DSI. The other authors have no conflicts of interests to disclose., (© 2024 The Author(s).)

The Dutch Drug Rediscovery Protocol (DRUP) and the Australian Cancer Molecular Screening and Therapeutic (MoST) Program are similar nonrandomized, multidrug, pan-cancer trial platforms that aim to identify signals of clinical activity of molecularly matched targeted therapies or immunotherapies outside their approved indications. Here, we report results for advanced or metastatic cancer patients with tumors harboring cyclin D-CDK4/6 pathway alterations treated with CDK4/6 inhibitors palbociclib or ribociclib. We included adult patients that had therapy-refractory solid malignancies with the following alterations: amplifications of CDK4, CDK6, CCND1, CCND2 or CCND3, or complete loss of CDKN2A or SMARCA4. Within MoST, all patients were treated with palbociclib, whereas in DRUP, palbociclib and ribociclib were assigned to different cohorts (defined by tumor type and alteration). The primary endpoint for this combined analysis was clinical benefit, defined as confirmed objective response or stable disease ≥16 weeks. We treated 139 patients with a broad variety of tumor types; 116 with palbociclib and 23 with ribociclib. In 112 evaluable patients, the objective response rate was 0% and clinical benefit rate at 16 weeks was 15%. Median progression-free survival was 4 months (95% CI: 3-5 months), and median overall survival 5 months (95% CI: 4-6 months). In conclusion, only limited clinical activity of palbociclib and ribociclib monotherapy in patients with pretreated cancers harboring cyclin D-CDK4/6 pathway alterations was observed. Our findings indicate that monotherapy use of palbociclib or ribociclib is not recommended and that merging data of two similar precision oncology trials is feasible., (© 2023 UICC.)

Alpelisib is a specific oral PI3K inhibitor used combined with fulvestrant for the treatment of patients with HR+/HER2-/PIK3CA-mutated metastatic breast cancer. Adverse drug reactions with alpelisib are common, including hyperglycemia and rash. Here we describe extraordinary and life-threatening reactions beyond skin rash in two patients with progressive PIK3CA-mutated metastatic cancer in whom alpelisib was initiated. Case-A (vaginal cancer): After 10 days on treatment, she developed dry eyes, generalized rash and itching. Alpelisib was interrupted and symptomatic treatment initiated. Because of an initial tumor response, a rechallenge was done. Ninety minutes after a reduced dose of alpelisib, she developed an anaphylactic reaction with angioedema, hypotension, and skin rash. Case-B (breast cancer): After 11 days on treatment, she developed skin rash and alpelisib was interrupted. At re-initiation, she felt tingles in her face and ears and some skin erythema. Given the mild rash, a second rechallenge with premedication was performed. Ninety minutes after a reduced dose of alpelisib, she developed a type-1 allergic reaction with angioedema, tingles, and skin rash. In both cases, a type-1 allergic reaction was diagnosed and symptomatic treatment was initiated, alpelisib was permanently discontinued and the patients fully recovered the next week(s). This report underlines the critical importance to consider type-I allergic reactions in the differential diagnosis in cases of rash associated with alpelisib. Even if a reaction develops after days on treatment, a type-I allergic reaction cannot be excluded. A rechallenge can be dangerous and should always be well contemplated or even avoided., (© The Author(s) 2023. Published by Oxford University Press.)

Background: In this study we aimed to evaluate the efficacy and safety of the PD-L1 inhibitor durvalumab across various mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H) tumours in the Drug Rediscovery Protocol (DRUP). This is a clinical study in which patients are treated with drugs outside their labeled indication, based on their tumour molecular profile., Patients and Methods: Patients with dMMR/MSI-H solid tumours who had exhausted all standard of care options were eligible. Patients were treated with durvalumab. The primary endpoints were clinical benefit ((CB): objective response (OR) or stable disease ≥16 weeks) and safety. Patients were enrolled using a Simon like 2-stage model, with 8 patients in stage 1, up to 24 patients in stage 2 if at least 1/8 patients had CB in stage 1. At baseline, fresh frozen biopsies were obtained for biomarker analyses., Results: Twenty-six patients with 10 different cancer types were included. Two patients (2/26, 8%) were considered as non-evaluable for the primary endpoint. CB was observed in 13 patients (13/26, 50%) with an OR in 7 patients (7/26, 27%). The remaining 11 patients (11/26, 42%) had progressive disease. Median progression-free survival and median overall survival were 5 months (95% CI, 2-not reached) and 14 months (95% CI, 5-not reached), respectively. No unexpected toxicity was observed. We found a significantly higher structural variant (SV) burden in patients without CB. Additionally, we observed a significant enrichment of JAK1 frameshift mutations and a significantly lower IFN-γ expression in patients without CB., Conclusion: Durvalumab was generally well-tolerated and provided durable responses in pre-treated patients with dMMR/MSI-H solid tumours. High SV burden, JAK1 frameshift mutations and low IFN-γ expression were associated with a lack of CB; this provides a rationale for larger studies to validate these findings., Trial Registration: Clinical trial registration: NCT02925234. First registration date: 05/10/2016., (© 2023. The Author(s).)

DNA mismatch repair-deficient (MMR-d) cancers present an abundance of neoantigens that is thought to explain their exceptional responsiveness to immune checkpoint blockade (ICB) 1,2 . Here, in contrast to other cancer types 3-5 , we observed that 20 out of 21 (95%) MMR-d cancers with genomic inactivation of β2-microglobulin (encoded by B2M) retained responsiveness to ICB, suggesting the involvement of immune effector cells other than CD8 + T cells in this context. We next identified a strong association between B2M inactivation and increased infiltration by γδ T cells in MMR-d cancers. These γδ T cells mainly comprised the Vδ1 and Vδ3 subsets, and expressed high levels of PD-1, other activation markers, including cytotoxic molecules, and a broad repertoire of killer-cell immunoglobulin-like receptors. In vitro, PD-1 + γδ T cells that were isolated from MMR-d colon cancers exhibited enhanced reactivity to human leukocyte antigen (HLA)-class-I-negative MMR-d colon cancer cell lines and B2M-knockout patient-derived tumour organoids compared with antigen-presentation-proficient cells. By comparing paired tumour samples from patients with MMR-d colon cancer that were obtained before and after dual PD-1 and CTLA-4 blockade, we found that immune checkpoint blockade substantially increased the frequency of γδ T cells in B2M-deficient cancers. Taken together, these data indicate that γδ T cells contribute to the response to immune checkpoint blockade in patients with HLA-class-I-negative MMR-d colon cancers, and underline the potential of γδ T cells in cancer immunotherapy., (© 2023. The Author(s).)

Competing Interests: EFS reports grants form AstraZeneca, Bristol Myers Squibb, Boehringer Ingelheim, Bayer, Merck Sharp & Dphme, Eli Lilly, Daiichi Sankyo, Roche, Novartis, Takeda, Pharmamar; received consulting fees from Eli Lilly; and received payments or honoraria for lectures, presentations, speakers’ bureaus, manuscript writing, or educational events for Boehringer Ingelheim, AstraZeneca, Daiichi Sankyo, and Novartis, all outside the submitted work. EEV reports grants from AstraZeneca, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Clovis Oncology, GlaxoSmithKline, Merck Sharp & Dohme, Novartis , Pfizer, Roche, and Sanofi, all outside the submitted work. All other authors declare no competing interests. The DRUG Access Protocol is supported by all participating pharmaceutical companies: Bayer, Roche, and Sanofi. No company had a role in writing of the manuscript or decision to submit it for publication. EEV, HJB, and EFS led the DRUG Access Protocol trial as principal investigators. HG and HMWV functioned as co-principal investigators for the trial. LJZ and SBvWvD-K wrote the manuscript. LJZ, GFdW, and BSG coordinated the trial. SBvWvD-K and AAMGP-vR functioned as representatives on behalf of the health insurance companies during trial design. LT, THLT, and JEdB represented the Dutch National Health Care Institute during trial design. NB, ANMW, FALME, and EFS functioned as representatives of the Dutch Medical Societies for Oncology, Pulmonology and Haematology during trial design. LJZ and SBvWvD-K contributed equally as first authors.