anti-PD1 Monotherapy Research Articles

Clinical spectrum and evolution of immune-checkpoint inhibitors toxicities over a decade—a worldwide perspective

Immune-checkpoint inhibitors (ICI) have revolutionized cancer treatment by harnessing the immune system but ICI can induce life-threatening immune-related adverse events (irAE) affecting every organ. We extracted irAE from VigiBase, the international pharmacovigilance database, first reported in 2008 until 01/2023 to characterize irAE reporting trends, clinical features, risk factors and outcomes. We distinguished 25 types of irAE (n=50,347cases, single irAE/case in 84.9%). Cases mainly involved anti-PD1 (programmed-death-1) monotherapy (62.4%) in male (61.7%) aged 64.3±12.6 years. After 2020 vs. prior to 2016, proportion of anti-CTLA4 (Cytotoxic-T-Lymphocyte-Antigen-4) monotherapy prescription almost vanished (1.6% vs. 47%, respectively) contrasting with increased use of anti-PDL1 (PD1-ligand) monotherapy (18% vs. 0.9%) and anti-CTLA4+anti-PD(L)1 combination (20% vs. 8.9%). Anti-LAG3 (Lymphocyte-Activation-Gene-3) prescription was limited (<1%) in the studied timeframe. After 2020, over 14 different cancer types were treated vs. almost exclusively melanoma and lung cancers before 2016. Overall, the most reported irAE were skin reactions (22.9%), pneumonitis (18.5%), enterocolitis (14.4%) and thyroiditis (12.1%). ICI-myotoxicities (6.6%) included myositis, myocarditis and myasthenia-gravis like syndrome and were the most overlapping irAE (up to 30% overlap, vs. <3% in general for other inter-irAE overlap). The top factors associated with specific irAE (odds-ratio>5) were presence of thymic cancer for ICI-myotoxicities or hepatitis; presence of melanoma for vitiligo, uveitis or sarcoidosis; specific types of ICI regimen (anti-LAG3 for meningitis, anti-CTLA4 for hypophysitis); and specific reporting regions (eastern Asia for cholangitis). Median time-to-onset ranged from 31 to 273 days, being shortest for myotoxicities and most delayed for skin-bullous auto-immune reactions. Overall fatality was highest for myocarditis=27.6%, myasthenia=23.1%, severe cutaneous adverse reactions (SCAR)=22.1%, myositis=21.9%, pneumonitis=21%, and encephalomyelitis=18%; generally decreasing after 2020, except for myasthenia and SCAR. When reported, irAE recurrence rate after rechallenge was 28.9% (n=275/951). This up-to-date comprehensive worldwide pharmacovigilance study defines the spectrum, characteristics, and evolution of irAE reporting summarizing over a decade of use. Multiple risk factors and clinical peculiarities for specific irAE have been identified as signals to guide clinical practice and future research. Paul Gougis was supported by the academic program: "Contrats ED: Programme blanc Institut Curie PSL" for the conduct of his PhD. Baptiste Abbar was supported by "the Fondation ARC Pour le Rechercher Sur le Cancer". The RT2L research group (Institut Curie) was supported by the academic program "SHS INCa", Sanofi iTech award, and by Monoprix∗.

Abstract 1446: Gastric cancer with microsatellite instability: Ex vivo generation of syngeneic mouse models

Abstract The DNA mismatch repair (MMR) system is a highly conserved pathway crucial for maintaining the genomic integrity. MMR impairment in sporadic tumors is due to MLH1 epigenetic silencing or mutations in other MMR genes (such as MSH2, MSH6, PMS2) and leads to microsatellite instability (MSI). Two independent molecular classifications reported the existence of a MSI subgroup in gastric cancer (GC), including 22-23% of all cases. GC MSI inter and intra-tumoral heterogeneity represents a significant challenge for precise patient stratification and treatment. Even if MSI status in GC is usually associated with a good prognosis, some reports described a subpopulation of MSI GC patients displaying a worse outcome. Moreover, while clinical trials testing immune checkpoint inhibitors in MSI tumors showed effectiveness across all treatment lines, the outcomes in GC patients were not as remarkable as in other cancer types. From the analysis of MSI GC patients enrolled in phase III clinical trials testing anti-PD1 monotherapy, it emerged that nearly half of the tumors are intrinsically resistant and complete and long-lasting responses are achieved in very few cases. Tumor mouse immunocompetent models allow to mimic the complex interactions between a fully functional immune system and a developing tumor. MSI GC syngeneic mouse models could thus represent a valuable tool to better understand the molecular complexity and predict the clinical behavior of this subgroup. To obtain MSI GC mouse models, we generated non-transformed organoids from normal gastric mucosa of BALB/c mice as a starting point for the induction of a neoplastic transformation ex vivo. To induce MMR deficiency, we inactivated either Mlh1 or Msh2 genes using CRISPR/Cas9 genome editing. Importantly, we did not introduce any other alteration in known oncogenes and tumor suppressor genes, thus allowing the natural emergence of driver mutations in the context of the genetic instability. Over time, MMR deficient models, but not the WT controls, exhibited MSI and increased their mutational burden. Furthermore, when cultured in stringent culture conditions (two-dimensional culture, growth factor deprivation), only MMR deficient cells generated tumor masses upon subcutaneous injection in immunodeficient NOD SCID mice. Importantly, cells retrieved from the tumor masses (n = 8) exhibited mutations in a relevant fraction of genes associated with the MSI subgroup by TCGA (21 out of 35) – including Kras, Arid1a, Erbb3 and Tpr53 – thus offering a good representation of the human MSI GC mutational landscape. Given the immunogenicity of the Cas9 protein, we finalized our models optimizing the genome editing protocol to avoid a persistent Cas9 expression. Cas9-free MMR deficient models were able to generate tumors in immunocompetent BALB/c mice, thus representing a valuable resource to investigate tumor development, progression and responses to immunotherapy in vivo. Citation Format: Daniela Conticelli, Gabriele Picco, Cristina Migliore, Claudia Orrù, Fabrizio Maina, Emanuela Boccuni, Simona Corso, Silvia Giordano. Gastric cancer with microsatellite instability: Ex vivo generation of syngeneic mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1446.

T-Cell Subtypes and Immune Signatures in Cutaneous Immune-Related Adverse Events in Melanoma Patients under Immune Checkpoint Inhibitor Therapy.

Immune checkpoint inhibition (ICI) improves outcomes in melanoma patients, but associated T-cell activation frequently leads to immune-related cutaneous adverse events (cutAEs). To dynamically identify T-cell subtypes and immune signatures associated with cutAEs, a pilot study was performed in stage III-IV melanoma patients using blood samples for flow cytometry and cytokine analysis. Blood samples were taken from patients before initiation of ICI (naive), at the onset of a cutAE, and after 6 months of ICI treatment. Overall, 30 patients were treated either with anti-PD1 monotherapy or with anti-PD-1/anti-CTLA-4 combination therapy. Flow cytometry analysis of PBMCs showed that ICI induced an overall shift from a Th2 towards a Th1 profile. Twelve patients (40%) developed cutAEs, which were associated with increased Th22 cells and Th17 cells, supported by a tendency to have elevated Th17/Th22-associated cytokines such as IL-17A, IL-22 and IL-23 levels in the plasma. Cytokine signatures specific for urticaria and T-cell-mediated cutAEs were identified in the plasma of patients by a bead-based assay. IL-10 was elevated in non-responders and, interestingly, during cutAEs. In conclusion, we identified distinct immune signatures based on the Th17/Th22 pathway in cutAEs, both in PBMCs and plasma. In addition, our finding of upregulated IL-10 during cutAEs supports the notion of treating these patients early and adequately to avoid implications for the overall outcome.

Thermal Ablation Combined with Immune Checkpoint Blockers: A 10-Year Monocentric Experience.

We report a 10-year experience in cancer therapy with concomitant treatment of percutaneous thermal ablation (PTA) and immune checkpoint blockers (ICBs). This retrospective cohort study included all patients at a single tertiary cancer center who had received ICBs at most 90 days before, or 30 days after, PTA. Feasibility and safety were assessed as the primary outcomes. The procedure-related complications and immune-related adverse events (irAEs) were categorized according to the Common Terminology Criteria for Adverse Events v5.0 (CTCAE). Efficacy was evaluated based on overall survival (OS), progression-free survival (PFS), and local progression-free survival (LPFS) according to the indication, ablation modality, neoplasm histology, and ICB type. Between 2010 and 2021, 78 patients (57% male; median age: 61 years) were included. The PTA modality was predominantly cryoablation (CA) (61%), followed by radiofrequency ablation (RFA) (31%). PTA indications were the treatment of oligo-persistence (29%), oligo-progression (14%), and palliation of symptomatic lesions or prevention of skeletal-related events (SREs) (56%). Most patients received anti-PD1 ICB monotherapy with pembrolizumab (n = 35) or nivolumab (n = 24). The feasibility was excellent, with all combined treatment performed and completed as planned. Ten patients (13%) experienced procedure-related complications (90% grade 1-2), and 34 patients (44%) experienced an irAE (86% grade 1-2). The only factor statistically associated with better OS and PFS was the ablation indication, favoring oligo-persistence (p = 0.02). Tumor response was suggestive of an abscopal effect in four patients (5%). The concomitant treatment of PTA and ICBs within 2-4 weeks is feasible and safe for both palliative and local control indications. Overall, PTA outcomes were found to be similar to standards for patients not on ICB therapy. While a consistently reproducible abscopal effect remains elusive, the safety profile of concomitant therapy provides the framework for continued assessment as ICB therapies evolve.

L-DOS47 Elevates Pancreatic Cancer Tumor pH and Enhances Response to Immunotherapy.

Acidosis is an important immunosuppressive mechanism that leads to tumor growth. Therefore, we investigated the neutralization of tumor acidity to improve immunotherapy response. L-DOS47, a new targeted urease immunoconjugate designed to neutralize tumor acidity, has been well tolerated in phase I/IIa trials. L-DOS47 binds to CEACAM6, a cell-surface protein that is highly expressed in gastrointestinal cancers, allowing urease to cleave endogenous urea into two NH4+ and one CO2, thereby raising local pH. To test the synergetic effect of neutralizing tumor acidity with immunotherapy, we developed a pancreatic orthotopic murine tumor model (KPC961) expressing human CEACAM6. Using chemical exchange saturation transfer-magnetic resonance imaging (CEST-MRI) to measure the tumor extracellular pH (pHe), we confirmed that L-DOS47 raises the tumor pHe from 4 h to 96 h post injection in acidic tumors (average increase of 0.13 units). Additional studies showed that combining L-DOS47 with anti-PD1 significantly increases the efficacy of the anti-PD1 monotherapy, reducing tumor growth for up to 4 weeks.

Management of acral lentiginous melanoma: current updates and future directions.

Acral lentiginous melanoma is a rare subtype of melanoma generally associated with poor outcomes, even when diagnosed at an early stage. The tumor genetic profile remains poorly understood, but it is known to have a suppressed immune environment compared to that of non-acral cutaneous melanomas, which limits therapy options. There is significant attention on the development of novel therapeutic approaches, although studies are limited due to disease rarity. For local disease, wide local excision remains the standard of care. Due to frequent under-staging on preoperative biopsy, wider margins and routine sentinel lymph node biopsy may be considered if morbidity would not be increased. For advanced disease, anti-PD1 monotherapy or combination therapy with anti-PD1 and anti-CTLA4 agents have been used as first-line treatment modalities. Anti-PD1 and anti-CTLA4 combination therapies have been shown to be particularly beneficial for patients with BRAF-mutant acral lentiginous melanoma. Other systemic combination regimens and targeted therapy options may be considered, although large studies with consistent results are lacking. Regional and intralesional therapies have shown promise for cutaneous melanomas, but studies generally have not reported results for specific histologic subtypes, especially for acral melanoma. Overall, the unique histologic and genetic characteristics of acral lentiginous melanoma make therapy options significantly more challenging. Furthermore, studies are limited, and data reporting has been inconsistent. However, more prospective studies are emerging, and alternative therapy pathways specific to acral lentiginous melanoma are being investigated. As further evidence is discovered, reliable treatment guidelines may be developed.

Efficiency and safety of hepatic arterial infusion chemotherapy (HAIC) combined with anti-PD1 therapy versus HAIC monotherapy for advanced hepatocellular carcinoma: A multicenter propensity score matching analysis.

To investigate the clinical efficacy and safety of combination therapy of hepatic arterial infusion chemotherapy (HAIC) and anti-programmed cell death protein-1 (PD-1) therapy in the treatment of advanced hepatocellular carcinoma (HCC). In this retrospective clinical research, from March 2018 to December 2019, 1158 HCC patients categorized as BCLC stage C were reviewed for eligibility. We utilized propensity score matching (PSM) to mitigate initial disparities between the groups. The evaluation of the best tumor response was conducted in accordance with mRECIST 1.1 criteria. The difference in survival outcomes including overall survival (OS), progression-free survival (PFS), and objective response rate (ORR) between groups were compared. Following the eligibility review, 453 patients underwent a combined treatment of HAIC with PD1 inhibitors (HAIC-PD1 group), while 221 patients received HAIC monotherapy (HAIC group) met the inclusion criteria and were finally enrolled in this study. In the entire cohort, the HAIC-PD1 group exhibited significantly prolonged overall survival (median overall survival: 40.4 months vs. 9.7 months, p < 0.001) and progression-free survival (median progression-free survival: 22.1 months vs. 5.8 months, p < 0.001). By propensity score, patients were matched according to baseline differences, resulting in all 442 patients in group HAIC-PD1 (n = 221) and group HAIC (n = 221). After PSM adjustment, as well, the survival of the HAIC-PD1 group was still distinctly longer than the HAIC group (median overall survival time, 40.4 months vs 9.7 months, p < 0.001; median progression-free survival, 22.1 months vs 5.7 months, p < 0.001). Univariate and multivariable analysis demonstrated that AFP level, metastasis, and therapeutic schedule were independent predictive factors for overall survival. The combination therapy of HAIC and PD1 inhibitors successfully extended OS to advanced HCC patients and could be a better choice than HAIC monotherapy.

Abstract A035: Comparing the clinical and genomic landscapes of acral, mucosal, and cutaneous metastatic melanomas treated with immune checkpoint inhibitors

Abstract Background: Melanoma is a melanocytic malignancy that is classified into different subtypes, including cutaneous (CM), acral (AM), and mucosal melanoma (MM). Immune checkpoint inhibitors (ICI) targeting PD-1 and/or CTLA-4 have emerged as the standard of care for advanced metastatic melanoma. We investigated responses to ICIs, genomic profiles, and molecular differences among these different subtypes of melanoma. Methods: We performed a multi-center retrospective cohort study including patients with metastatic melanoma who received anti-PD1 +/- CTLA4 inhibitor ICI for metastatic disease. We employed the AACR GENIE (v13.1) cancer database, DepMap portal, and Enrichr web tool with MSigDB Hallmark 2020 database to analyze the incidence and distribution of significant alterations, differentially expressed genes, and pathway enrichment within distinct melanoma subtypes. Results: We identified 337 patients with advanced melanoma who received anti-PD1 +/- anti-CTLA4 for metastatic disease. CM was the most frequent melanoma subtype (81%), followed by MM (12%), and AM (8%). Patients with AM had the shortest OS and PFS CM (OS 3.4 years, PFS of 1.1 years), AM median (OS 1.4 years, PFS 3.8 months), and MM (OS 1.7 years, PFS 6 months; OS, P= 0.028; PFS P=0.029). Patients with CM or MM experienced longer OS with anti-PD1 +/- CTLA4 vs. anti-PD1 monotherapy, but no survival advantage was observed in patients with AM. In the GENIE dataset, we identified 2015/374/177 samples with CM/MM/AM, respectively. AM and MM patients were significantly more likely to be Female, Black or Asian than CM patients. BRAF V600 mutations were most frequent in CM (40%), followed by MM (7%) and AM (14%). However, MM and AM had an increase in alterations in cell cycle regulator genes. The incidence of CDK4 and CCND1 amplification, respectively was highest in AM (17%, 16%), followed by MM (6%, 6%) and CM (2%, 3%). We compared the pathways represented by differentially altered genes in AM vs. CM: G2M-Checkpoint (Q&amp;lt;0.05) and E2F targets (Q&amp;lt;0.05) pathways were enriched in AM. We also compared RNAseq data from n=4) AM and n=20 CM cell lines, and found the same pathways enriched amongst genes that were differentially expressed between AM and CM: G2M-Checkpoint (Q&amp;lt;0.01) and E2F targets (Q&amp;lt;0.01) Conclusions: Our findings highlight comparatively poor outcomes with ICIs in Acral Melanoma. AM has lower rates of actionable BRAF mutations; as such, very few patients with metastatic AM have access to effective 1st or 2nd line therapies. Thus, there is an urgent need to explore alternative therapeutic targets. Our data implicate cell cycle inhibitors as potentially important components of novel treatment strategies that could augment immunotherapy efficacy for patients with metastatic AM. Citation Format: Sadaf Solati, April A. N. Rose, Anna Spreafico, Adrian Sacher, Denis Yahiaoui, Wilson H. Miller. Comparing the clinical and genomic landscapes of acral, mucosal, and cutaneous metastatic melanomas treated with immune checkpoint inhibitors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A035.

Abstract A172: TP-317, a first-in-class resolvin E1 small molecule, drives adjuvant efficacy in solid tumors by engaging innate and adaptive anti-tumor immunity in the tumor microenvironment (TME) and has neoadjuvant potential

Abstract Background: TP-317 is a novel salt of resolvin E1 (RvE1), an endogenous lipid agonist of ChemR23 that stimulates tumor debris phagocytosis/clearance by myeloid cells (Sulciner et al., 2018, J.Exp.Med). We recently reported TP-317 anti-tumor efficacy in murine solid tumors as monotherapy and in combination with immune checkpoint inhibitors (ICI) and chemotherapy (Kipper, 2023, Can. Res, 83 (7_Supp: 1135). Here we elaborate on the mechanism of action (MOA) of TP-317 in the adjuvant setting and report TP-317 efficacy in a neoadjuvant regimen Methods: 125-240 mm3 established subcutaneous murine melanoma (B16F10) and pancreatic (Panc02-H7; KPC) tumors were treated with placebo, TP-317 or ICI and tumors excised at 12-14 days for bulk RNAseq or flow cytometry. Placebo, TP-317 (300 ug/kg s.c. 2 hr prior to and Q6D after resection), cisplatin (5 mg/kg i.p. 24 hrs prior to resection) or anti-PD1 (8 mg/kg i.p. 24 hr prior to resection only) or TP-317 + anti-PD1 were evaluated in the LLC lung tumor model with tumors resected when reaching ~ 1500 mm3. Endpoints were lung/lymph node metastases or survival. Results: RNAseq analysis showed that adjuvant TP-317 broadly engages innate (macrophage, dendritic, NK cells) and adaptive (CD8, CD4, B cells) immune pathways in the TME of PANC2-H7, KPC and B16F10 models. Depletion studies suggest TP-317 efficacy is CD8- and NK cell-dependent, consistent with the RNAseq data and flow cytometry, which confirmed expression of ChemR23 (RvE1 receptor) on M1/M2 macrophages, conventional cDC1/cDC2, NK and lymphoid subsets. In the TME of PANC2-H7, KPC and B16-F10 models, TP-317 induced a gene signature with upregulated IFNg responses, effector CD8/NK receptors, antigen-presenting pathways, cDC1/NK cell cross-talk, and chemokines/cytokines involved in anti-tumor immunity. In the B16F10 model TP-317 + dual ICI combined therapy synergistically upregulated an IFNg response signature relative to dual ICI therapy. In the LLC resection model, TP-317 monotherapy reduced lung (p&amp;lt;0.05) and lymph node metastases (p&amp;lt;0.01) 19 days post-resection, but cisplatin was not effective. Neoadjuvant cisplatin or anti-PD1 monotherapy did not improve survival relative to placebo, but TP-317 combined with neoadjuvant anti-PD1 induced long term survival (&amp;gt;100 days) in 3 of 7 treated mice (p &amp;lt;0.05 vs placebo or anti-PD1). Conclusions: In adjuvant therapy of murine tumors, TP-317 broadly modulates innate/adaptive immune cell compartments in the TME, consistent with resetting the immunogenic tone and favoring anti-tumor immunity. Mechanistic synergy was observed for TP-317 combined with dual ICI therapy. TP-317 monotherapy shows metastasis control when initated prior to surgical resection and long term survival when combined with neoadjuvant anti-PD1 in the LLC model of NSCLC. Citation Format: John F Parkinson, Eva Rothenberger, Abigail Kelly, Diane Bielenberg, Ahmed Attaya, Sui Huang, Lance Pflieger, Wayne Klohs, Gary Mathias, Dipak Panigrahy. TP-317, a first-in-class resolvin E1 small molecule, drives adjuvant efficacy in solid tumors by engaging innate and adaptive anti-tumor immunity in the tumor microenvironment (TME) and has neoadjuvant potential [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A172.

IMMU-24. SALVAGE IMMUNOTHERAPIES FOR REPLICATION REPAIR DEFICIENT (RRD) HIGH-GRADE GLIOMA FAILING ANTI-PD1 MONOTHERAPY: A REPORT FROM THE INTERNATIONAL RRD CONSORTIUM

Abstract BACKGROUND Initial response to immune checkpoint inhibition (ICI) for DNA replication-repair deficient high-grade glioma (RRD-HGG) is encouraging. However, clinical/biologic implications of immune-directed approaches after failing ICI-monotherapy remain unknown. METHODS We performed an international study of patients managed using central review/treatment recommendations (2015-2021). Salvage after anti-PD1 failure included re-irradiation where feasible, and addition of anti-CTLA4 (ipilimumab), or a MEK-inhibitor (MEKi). Outcomes included radiological response (iRANO), toxicity, second progression-free (PFS2) and overall survival (OS2). Companion biomarkers were performed centrally. RESULTS Twenty among 75 patients treated on anti-PD1 monotherapy are progression-free at a median follow-up of 44.6-months. For 55 patients with relapsed/progressive tumors, continuation of ICI (n=38) resulted in median OS2 of 11.6-months (51% alive) versus 1.2-months when ICI was discontinued (n=17; no survivors, p&amp;lt; 0.001). Addition of ipilimumab (n=24) resulted in response/stable disease in 75% with median OS2 of 12.1-months. High autoimmune toxicities (54%) were observed, particularly in constitutional mismatch-repair deficiency patients. The addition of MEKi led to response in 3/5 patients with prolonged survival. The addition of re-irradiation improved median OS2, especially in tumors with lower mutation burden (p=0.002), and those who received ipilimumab (median OS2=33-months). Several biological insights were gained. Increased CTLA4 expression explained responses to ipilimumab. Re-irradiation responses were attributed to the absence of radio-resistant indel signature (ID8). Early radiological ‘flare’ was observed in 33% on combined immunotherapy and re-radiation. MEKi responses were associated with reinvigoration of peripheral immune response. Finally, delayed, sustained responses were observed in ultra-hypermutant RRD-HGG exhibiting changes in somatic mutational spectra. CONCLUSION These data suggest that the continuous mutagenesis renders hypermutant RRD-HGG susceptible to checkpoint inhibitors beyond initial progression. The combination with re-irradiation and additional immune/targeted agents can maximize survival in these children and young adults. Future research should focus on biology-driven rational immunotherapy combinations that also result in lower toxicity to maximize patient benefit.

Combined Immunotherapy Improves Outcome for Replication-Repair-Deficient (RRD) High-Grade Glioma Failing Anti-PD-1 Monotherapy: A Report from the International RRD Consortium.

Hypermutant RRD-HGG are susceptible to checkpoint inhibitors beyond initial progression, leading to improved survival when reirradiation and synergistic immune/targeted agents are added. This is driven by their unique biological and immune properties, which evolve over time. Future research should focus on combinatorial regimens that increase patient survival while limiting immune toxicity. This article is featured in Selected Articles from This Issue, p. 201.

A single center case series of immune checkpoint inhibitor-induced type 1 diabetes mellitus, patterns of disease onset and long-term clinical outcome.

Type 1 diabetes mellitus (T1DM) is a rare, but serious immune-related adverse event (irAE) of immune checkpoint inhibitors (ICIs). Our goal was to characterize treatment outcomes associated with ICI-induced T1DM through analysis of clinical, immunological and proteomic data. This was a single-center case series of patients with solid tumors who received ICIs and subsequently had a new diagnosis of T1DM. ICD codes and C-peptide levels were used to identify patients for chart review to confirm ICI-induced T1DM. Baseline blood specimens were studied for proteomic and immunophenotypic changes. Between 2011 and 2023, 18 of 3744 patients treated at Huntsman Cancer Institute with ICIs were confirmed to have ICI-induced T1DM (0.48%). Eleven of the 18 patients received anti-PD1 monotherapy, 4 received anti-PD1 plus chemotherapy or targeted therapy, and 3 received ipilimumab plus nivolumab. The mean time to onset was 218 days (range 22-418 days). Patients had sudden elevated serum glucose within 2-3 weeks prior to diagnosis. Sixteen (89%) presented with diabetic ketoacidosis. Three of 12 patients had positive T1DM-associated autoantibodies. All patients with T1DM became insulin-dependent through follow-up. At median follow-up of 21.9 months (range 8.4-82.4), no patients in the melanoma group had progressed or died from disease. In the melanoma group, best responses were 2 complete response and 2 partial response while on active treatment; none in the adjuvant group had disease recurrence. Proteomic analysis of baseline blood suggested low inflammatory (IL-6, OSMR) markers and high metabolic (GLO1, DXCR) markers in ICI-induced T1DM cohort. Our case series demonstrates rapid onset and irreversibility of ICI-induced T1DM. Melanoma patients with ICI-induced T1DM display excellent clinical response and survival. Limited proteomic data also suggested a unique proteomic profile. Our study helps clinicians to understand the unique clinical presentation and long-term outcomes of this rare irAE for best clinical management.

Therapeutic and Adverse Effect of Anti-PD1 Immunotherapy in Melanoma: A Retrospective, Single-Institute Study of 222 Patients.

The introduction of immuno- and targeted therapeutic modalities meant a breakthrough step in the therapy of melanoma. As a checkpoint inhibitor, the more effective and less toxic anti-PD1 therapy followed an anti-CTLA4 approach. From our patient pool, 222 advanced melanoma cases were selected, where anti-PD1 (pembrolizumab, nivolumab) therapy was initiated between March 2015 and December 2020. During our retrospective analysis, the efficacy and safety of the therapy were assessed. The median follow-up was 16 months (interval: 0-64 months), and 150 patients (67.6%) received therapy in the first line, while second and third line therapy was performed among 72 patients (32.4%) for the median of 7.0 months (0-60). In 50 cases, BRAF mutations were detected. Ninety-six patients showed objective response (11.3% CR, 32.0% PR). The median PFS was 10.0 months (0-60), and the median OS was 23.0 months (0-64). Autoimmune side effects were found in 79 patients (35.5%); grade 3 occurred in 6.3% of the cases, while 1 patient died due to fulminant pneumonitis (0.25%). Although the range of immunotherapeutic options is getting wider, in the management of melanoma patients, anti-PD1 monotherapy remains an important, effective, and safe method. However, significant correlation was found between the immune-related side effects and therapeutic efficacy.

IMMU-08. SALVAGE IMMUNOTHERAPIES FOR REPLICATION REPAIR DEFICIENT (RRD) HIGH-GRADE GLIOMA FAILING ANTI-PD1 MONOTHERAPY: AN IRRDC REPORT

Abstract BACKGROUND Although the initial response to immune-checkpoint inhibition (ICI) for patients with DNA replication-repair deficient high-grade glioma (RRD-HGG) is encouraging, the role of immune-based salvage approaches for those progressing on anti-PD1 monotherapy is unknown. METHODS We performed an international registry study of patients managed using central molecular, genomic, radiological review and treatment recommendations between 2015-2021. Post-progression treatment included re-irradiation where feasible, and continuation of anti-PD1 with anti-CTLA4 (ipilimumab), or a MEK-inhibitor (MEKi). Outcomes included radiological response (iRANO), toxicity, second progression-free (PFS2) and overall survival (OS2). Companion biomarkers were performed centrally. RESULTS Among 75 patients with RRD-HGG receiving PD-1 blockade, 20 are progression-free at a median follow-up of 44.6-months. For 55 patients with relapsed/progressive tumors, continuation of ICI (n=38) resulted in median OS2 of 11.6-months (51% alive) versus 1.2-months when ICI was discontinued (n=17; no survivors, p&amp;lt;0.001). The combination of ipilimumab/nivolumab (n=24) resulted in response/stable disease in 75% with median OS2 of 12.1-months but high autoimmune toxicities (54%). The addition of MEKi led to response in 3/5 patients with prolonged survival. The addition of re-irradiation improved median OS2, especially in tumors with lower mutation burden (p=0.002), and those who received ipilimumab (median OS2=33-months). Several biological insights were gained. Early radiological ‘flare’ in 33% of RRD-HGG on combined immunotherapy and radiation were associated with immunogenic radiation induced signatures. MEKi responses were associated with reinvigoration of peripheral immune response. Finally, delayed, sustained responses were observed in ultra-hypermutant RRD-HGG exhibiting changes in somatic mutational spectra. CONCLUSION These data suggest that the continuous mutagenesis renders hypermutant RRD-HGG susceptible to checkpoint inhibitors beyond initial progression. The combination with re-irradiation and additional immune/targeted agents can maximize survival in these children and young adults. Future research should focus on biology-driven rational immunotherapy combinations that also result in lower toxicity to maximize patient benefit.

MDB-12. TRANS-SPECIES ANALYSIS OF REPLICATION-REPAIR DEFICIENT (RRD) MEDULLOBLASTOMA AND RESPONSE TO IMMUNE-CHECKPOINT INHIBITION: AN IRRDC REPORT

Abstract BACKGROUND Replication-repair deficiency (RRD) stemming from mismatch repair and polymerase-proofreading gene defects (MMRD/PPD) lead to hypermutant childhood cancers, most frequently brain tumors. While medulloblastoma is reported, the clinical, genomic and immune landscape remains unknown. METHODS We analysed the genome, methylome, transcriptome (bulk, single-nuclei) and immune-microenvironment of the largest cohort of RRD-medulloblastoma patients enrolled by the International RRD Consortium, and correlated these to clinical outcomes. RRD mice-models were used to preclinically assess response to immunotherapy. RESULTS RRD-medulloblastoma (n=40) were enriched for anaplasia (55%) and localised disease (85%). Methylation/nano-string-based subgrouping failed to classify 40%, while the remaining clustered with the SHH-subgroup. Copy-number changes were notably infrequent (&amp;lt;20%). All tumors harboured hypermutation and microsatellite instability in contrast to non-RRD controls (p&amp;lt;0.0001). Pathogenic variants were frequent in POLE/POLD1 (80%), TP53 (48%) and SHH-pathway genes (PTCH1, SUFU, SMO: 56%). Interestingly, some tumors additionally had glioma-driver alterations (ATRX, NF1: ~50%), similar to RRD cerebellar glioblastoma, but distinct from both non-RRD medulloblastoma (n=791) and hemispheric glioblastoma (n=733) controls. Moreover, although bulk-transcriptome matched non-RRD SHH-medulloblastoma, single-nuclei analyses suggested an earlier cell-of-origin potentially explaining the heterogenous phenotypes resulting from the driver mutations. Uniquely, immune analyses (gene expression and immunohistochemistry) demonstrated high intra-tumoral CD8 T-cell infiltration. Three-year progression-free survival was 60%. Outcome was worse for RRD-medulloblastoma harbouring TP53-mutation (p=0.04) and failing subgroup-classification (p=0.004). Nestin/Cre MSH2-/- POLE;p.S459F mice developing medulloblastoma recapitulated human disease and demonstrated response to anti-PD1 monotherapy. Recurrent/progressive human tumors including those harbouring TP53-mutations exhibited radiological responses to anti-PD1 monotherapy, which was associated with prolonged ongoing survival in comparison to those not treated with checkpoint-inhibitors (p=0.02). CONCLUSIONS Hypermutant RRD-medulloblastoma reveal heterogenous phenotypes due to unique spectrum of driver mutations and an early cell of origin. Their immune-hot microenvironment allows successful salvage treatment with checkpoint-inhibitors for those failing chemo-radiation, including the high-risk SHH/TP53-mutant and unclassified subgroups.

Non-comparative, open-label, international, multicenter phase I/II study of nivolumab (NIVO) ± ipilimumab (IPI) in patients (pts) with recurrent/metastatic merkel cell carcinoma (MCC) (CheckMate 358).

9506 Background: MCC is a rare and aggressive skin cancer. Programmed death-ligand 1 (PD-L1) is often upregulated in MCC and blockade of PD-L1 or its receptor, PD-1, has improved survival for patients with metastatic MCC. Anti–PD-1 combined with anti–CTLA-4 has been reported to improve outcomes over anti–PD-1 monotherapy (NCT03071406; Kim S et al., Lancet 2022), however further investigation is needed. CheckMate 358 (NCT02488759) assessed NIVO ± IPI in 2 non-randomized MCC cohorts. Methods: Eligible pts had recurrent or metastatic MCC, ≤ 2 prior therapies, ECOG performance status (PS) 0–1, and no prior immune checkpoint inhibitor (ICI) therapy. Pts were eligible regardless of PD-(L)1 status. Pts received NIVO 240 mg Q2W or NIVO 3 mg/kg Q2W + IPI 1 mg/kg Q6W for ≤ 24 months (m) or until disease progression, unacceptable toxicity, or consent withdrawal. Imaging was conducted Q8W in year 1 and Q12W thereafter. Planned sample sizes were 23 pts for NIVO and 40 pts for NIVO + IPI. The primary endpoint was investigator-assessed objective response rate (ORR). Secondary endpoints included duration of response (DOR), investigator-assessed progression-free survival (PFS), and overall survival (OS). Results: 68 pts received NIVO (n = 25) or NIVO + IPI (n = 43) with ≥ 24 m follow-up (median: NIVO, 62.5 m; NIVO + IPI, 24.4 m). In the NIVO arm, median age was 66 yrs (range, 27–88), 10 (40.0%) pts had ECOG PS of 1, and 15 (60.0%) were treatment-naive. In the NIVO + IPI arm, median age was 70 yrs (range, 48–85), 27 (62.8%) pts had ECOG PS of 1, and 33 (76.7%) were treatment-naive. Treatment duration was 15.8 m in the NIVO arm, and 7.9 m for NIVO and 6.0 m for IPI in the NIVO + IPI arm. Efficacy and safety outcomes are summarized in the table. ORR was 60.0% (95% CI, 38.7–78.9) in the NIVO arm and 58.1% (95% CI, 42.1–73.0) in the NIVO + IPI arm. The most common reasons for treatment discontinuation were disease progression (NIVO, 28.0%; NIVO + IPI, 32.6%) or study-drug toxicity (NIVO, 20.0%; NIVO + IPI, 25.6%). There was 1 study drug-related death in each arm (NIVO, pneumonitis; NIVO + IPI, gastrointestinal motility disorder). Conclusions: Both NIVO and NIVO + IPI show durable clinical efficacy in advanced MCC. While the non-randomized trial design limits comparisons between the arms, results do not suggest additional efficacy benefit with IPI added to NIVO. Higher incidence of grade 3/4 TRAEs observed in the combination arm could have resulted in shorter treatment duration. Clinical trial information: NCT02488759 . [Table: see text]

Imaging response to immune checkpoint inhibitors in patients with advanced melanoma: A retrospective observational cohort study.

e21524 Background: The association of objective imaging response with first line immune checkpoint inhibitor (ICI) therapy regimes in advanced melanoma remains uncharacterized in a real-world context. We compared likelihood of objective response between patients receiving first line anti-programmed cell death protein 1 (anti-PD1) monotherapies (pembrolizumab or nivolumab), or combination nivolumab with the cytotoxic T-cell lymphocyte-antigen 4 inhibitor ipilimumab and outlined the association between objective response and baseline characteristics and survival outcomes. Methods: We conducted a multi-center retrospective cohort analysis of advanced melanoma patients receiving first line ICI therapy from 2013-2020 in Alberta, Canada. Best imaging response was assessed by Response Evaluation Criteria in Solid Tumors, Version 1.1. The primary outcome was likelihood of objective imaging response (complete or partial response) between patients receiving anti-PD1 monotherapy and those receiving combination nivolumab-ipilimumab. Secondary outcomes were the identification of baseline characteristics associated with non-response and the association of imaging response with overall survival (OS) and time to next treatment (TTNT) endpoints. Results: Of the 255 patients included, 49/255 (19.2%) had complete response 112/255 (43.9%) had partial response, 28/255 (11.0%) had stable disease, and 66/255 (25.9%) had progressive disease. Median OS was not evaluable (NE) (95% CI NE-NE) for complete responders, NE (95% CI 52.93 months-NE) for partial responders, 21.30 months (95% CI 15.20 months-NE) for stable disease, and 7.72 months (95% CI 5.77-10.6 months) for progressive disease (log rank p &lt; 0.0001). A robust delineation of TTNT by imaging response was also seen. Likelihood of objective response was similar between patients treated with nivolumab-ipilimumab compared to those receiving anti-PD1 monotherapy (OR 1.87 95% CI 0.85-4.20, p = 0.124). Normal LDH level (OR 2.13; 95% CI 1.01-4.35, p = 0.047), non-mucosal primary site (OR 9.09; 95% CI 2.44-33.33, p &lt; 0.001), and absence of BRAF V600E mutation (OR 3.23; 95% CI 1.39-7.69, p = 0.007) were independently associated with likelihood of objective imaging response in multivariable analysis. Conclusions: In this real-world analysis, we demonstrate no significant difference in likelihood of objective response between patients treated with anti-PD1 monotherapy and combination nivolumab-ipilimumab, and demonstrate that a normal LDH level, non-mucosal primary site, and absence of BRAF V600E mutation are associated with response. Imaging response was also strongly associated with both OS and TTNT irrespective of therapy received. These results may help inform treatment selection, and aid in counseling of advanced melanoma patients treated with first line ICI therapy in a routine clinical practice setting.

WED-285 - Rechallenge with anti-PD1 monotherapy after checkpoint inhibitor hepatitis is associated with low rates of recurrence: a single centre study

WED-285 - Rechallenge with anti-PD1 monotherapy after checkpoint inhibitor hepatitis is associated with low rates of recurrence: a single centre study

Phase 2 trial of retifanlimab (anti–PD-1) in combination with INCAGN02385 (anti–LAG-3) and INCAGN02390 (anti–TIM-3) as first-line treatment in patients with PD-L1–positive recurrent/metastatic squamous cell carcinoma of the head and neck.

TPS6104 Background: Anti–PD-(L)1 therapies have improved clinical outcomes in PD-L1+ squamous cell carcinoma of the head and neck (SCCHN). However, many patients either do not respond or develop resistance, partly due to additional immune checkpoint receptors including LAG-3 and TIM-3, which are frequently coexpressed with PD-1 on tumor-infiltrating lymphocytes. In preclinical studies, LAG-3 and TIM-3 blockade showed synergistic activity with PD-1 inhibition, and triple blockade improves T-cell reinvigoration and antitumor efficacy over single/double combinations. Emerging clinical evidence also supports blockade of PD-1, LAG-3, and TIM-3 as a promising combination approach in checkpoint inhibitor–naive patients. This study aims to assess the efficacy and safety of the anti–PD-1 antibody, retifanlimab, in combination with INCAGN02385 (anti–LAG-3) and INCAGN02390 (anti–TIM-3) antibodies as first-line treatment in PD-L1+ recurrent or metastatic SCCHN. Methods: This randomized, double-blind, multicenter, phase 2 study (NCT05287113) includes patients with previously untreated, recurrent or metastatic, PD-L1+ (combined positive score [CPS] ≥1%) SCCHN and ECOG status of 0 or 1. Approximately 162 patients will be randomized 1:1:1 to receive (1) intravenous (IV) retifanlimab 500 mg every 4 weeks (Q4W) plus placebo controls, (2) retifanlimab plus IV INCAGN02385 350 mg Q2W plus placebo, or (3) retifanlimab plus INCAGN02385 plus IV INCAGN02390 400 mg Q2W. Patients will be stratified at randomization by LAG-3 expression (tumor proportion score ≥5% vs &lt; 5%), PD-L1 CPS (1%-19% vs ≥20%), and human papillomavirus p16 status (positive vs negative; oropharyngeal tumors only). Treatment will be administered in 4-week cycles for up to 2 years. The primary endpoint is progression-free survival (PFS; defined per Response Evaluation Criteria in Solid Tumors [RECIST] v1.1). Secondary endpoints are objective response rate per RECIST v1.1, duration of response, disease control, overall survival, and safety. Sample size calculation is based on a median PFS of 3 months, based on historical data for anti–PD-1 monotherapy in the first-line treatment setting for PD-(L)1+ advanced/metastatic SCCHN. PFS, overall survival, and duration of response data will be analyzed by the Kaplan-Meier method. Patient enrollment is ongoing. Clinical trial information: NCT05287113 .

Immunohistochemical expression of ER and p53 as predictive biomarkers of immunotherapy in endometrial cancer.

e17626 Background: Immune Checkpoint Inhibitors (ICIs), either as monotherapy or in combination with tyrosine kinase inhibitors (TKIs), were recently incorporated into the therapeutic guidelines for recurrent/metastatic endometrial cancer (EC). Microsatellite Instability (MSI) is the only biomarker to guide treatment. We evaluated the predictive significance of Estrogen Receptor (ER) and p53 expression. Methods: Medical charts of EC patients that received ICIs in our institution for advanced/metastatic disease were retrospectively reviewed. TP53 and ER expression were determined by immunohistochemistry. Survival analysis was performed using IBM SPSS statistics v.25. Results: Thirty-two patients were included in our analysis. The median age was 63.1 years (25th-75th percentile: 57.6 – 69.6). 62.5% of the patients had endometrioid histology, 21.9% serous histology and 15.6% of them displayed other histology. 46.9% of the patients had grade 1-2 tumors and 53.1% grade 3 tumors. 21.9% of them were diagnosed with stage 1-2 disease, while 78.1% presented with stage 3 disease. 62.5% received 0-1 prior lines of treatment and 37.5% of them received more than 2 prior lines. Molecular characteristics are presented in the table. All MSI-High patients received anti-PD1 monotherapy with a median PFS of 11.9 months (95% CI:2.3-21.5). Microsatellite Stable (MSS) patients received pembrolizumab-lenvatinib combination with median PFS 7.54 months (95% CI:2.6-11.5). ER positivity was associated with significant PFS benefit in both the ICI monotherapy group (11.9 vs. 0.63 months, p=0.061) and the group that received ICI/TKI combination (11.3 vs. 1.75 months, p=0.001). Analogous benefit was noted in the Overall Survival post start of IO or IO/TKI treatment (9.8 vs 0.6 months in MSI-high patients and 20.6 vs 5.9 months in MSS patients). ER-positivity remained an independent predictive factor favoring PFS in the Multivariate Cox regression analysis when adjusting for immunotherapy type, histology, and previous lines of therapy (HR=0.216, p=0.013). Conclusions: ER expression proved to be an independent prognostic factor regarding PFS in our cohort of patients. Further studies are needed to investigate the role of ER as a predictive biomarker for immunotherapy in EC. [Table: see text]