Retifanlimab is a humanized immunoglobulin G4 monoclonal antibody against programmed death 1 being investigated in several solid tumor types. We report final results from patients with recurrent microsatellite instability-high (MSI-H)/mismatch repair deficient (dMMR) endometrial cancer treated with retifanlimab in a POD1UM-101 expansion cohort.
Eligible patients (≥18 years; histologically proven/unresectable/recurrent, MSI-H/dMMR endometrial cancer; checkpoint inhibitor naive) received retifanlimab 500 mg intravenously every 4 weeks for ≤2 years. Primary endpoint was safety/tolerability.
At data cutoff (May 17, 2023), 76 patients had received at least one retifanlimab dose. Median (range) age was 67 (49-88) years; 88.2% of patients had recurrent metastatic disease and 80.3% had visceral metastases. Seventy-five patients (98.7%) had received at least one prior systemic therapy. Median retifanlimab exposure was 10.0 (0.03-25.9) months; 23 patients completed treatment. 38 patients (50.0%) had grade ≥3 treatment-emergent adverse events (TEAEs), most commonly anemia (n = 10 [13.2%]). 63 patients (82.9%) had treatment-related AEs (TRAEs; grade ≥3, n = 14 [18.4%]); most common was fatigue (n = 14 [18.4%]). Two patients had TEAEs that led to death; no TRAEs were fatal. 39 patients had objective responses (51.3%; 95% CI, 39.6-63.0%); 19 patients (25.0%) had complete response and 20 (26.3%) had partial response. Median progression-free survival was 12.2 months; 30 patients (76.9%) had duration of response (DOR) ≥12 months. Median DOR was not reached after median follow-up time of 26.0 months.
Retifanlimab was generally well tolerated and demonstrated encouraging anti-tumor activity in patients with pre-treated recurrent MSI-H/dMMR endometrial cancer.

OBJECTIVE: Patients with advanced penile squamous cell carcinoma (PSCC) have poor outcomes and very limited therapeutic options are available. Most PSCC cases have high PD-L1 expression, which is associated with worse prognosis. Immunotherapy targeting PD-L1 could benefit patients with PSCC. Our aim was to evaluate the efficacy and safety of the anti-PD-1 antibody retifanlimab in patients with advanced/metastatic PSCC.
METHODS: ORPHEUS was a single-arm, multicenter, phase 2 trial in 18 patients with advanced/metastatic PSCC, previously untreated with anti-PD-1/anti-PD-L1 agents. Patients received retifanlimab 500 mg intravenously every 4 wk for up to 2 yr. The primary endpoint was the objective response rate (ORR) according to Response Evaluation Criteria in Solid Tumors v1.1. Secondary endpoints included the clinical benefit rate (CBR), disease control rate, duration of response (DoR), time to response, progression-free survival (PFS), overall survival (OS), maximum tumor shrinkage, and safety. The Wilson method was used for the primary endpoint, and the Clopper-Pearson and Kaplan-Meier methods for secondary endpoints.
UNASSIGNED: Median follow-up was 7.2 mo. The ORR was 16.7% (95% confidence interval [CI] 5.8-39.2); three patients had a partial response. Median DoR was 3.3 mo (range 1.8-8.5). The CBR was 22.2% (95% CI 6.4-47.6%). Median PFS was 2.0 mo (95% CI 1.6-3.3) and median OS was 7.2 mo (95% CI 3.0-9.8). One patient (5.6%) experienced grade 3 treatment-related adverse events (AEs). There were no grade >= 4 treatment-related AEs. The small sample size is the main limitation.
CONCLUSIONS: Single-agent retifanlimab exhibited signals of clinical activity in advanced/metastatic PSCC, with no new safety signals. Further investigation of retifanlimab in this setting is warranted.
RESULTS: Advanced penile cancer of the squamous cell type is a rare tumor with poor prognosis. The aggressiveness of this cancer is usually associated with high levels of a protein called PD-L1. We investigated whether retifanlimab, an immunotherapy drug against PD-1, has activity against this type of penile cancer. Tumor regression or stabilization occurred in one-third of the patients and the side effects were manageable.

BACKGROUND: Retifanlimab is a humanized monoclonal antibody targeting programmed death protein-1, and INCB001158 is an oral arginase inhibitor. This phase Ib study investigated retifanlimab, INCB001158, and their combination in Japanese patients with advanced solid tumors.
METHODS: Patients received retifanlimab (500 mg every 4 weeks [Q4W] i.v.) or escalating doses of INCB001158 (75 or 100 mg twice daily [BID]) monotherapy in Part 1 and combination of retifanlimab (500 mg Q4W) and INCB001158 (100 mg BID) in Part 2. Primary endpoints were safety, tolerability, dose-limiting toxicities (DLTs), and determination of recommended phase II doses in Japanese patients.
RESULTS: Eighteen patients (retifanlimab or INCB001158 monotherapy and combination; n = 6 each) were enrolled at 2 sites in Japan. There were no DLTs, fatal adverse events (AEs), or discontinuations due to AEs. Rash (all grade 1) was the most common treatment-emergent AE with retifanlimab (n = 6). Treatment-related AEs were reported with retifanlimab (n = 4) or INCB001158 (n = 2) monotherapy and with combination (n = 4); an immune-related AE (thyroid disorder, grade 2) was reported with combination. Two responses were observed with retifanlimab monotherapy (1 complete, 1 partial) and 1 stable disease (SD), for an overall response rate of 33.3% (95% confidence interval [CI], 4.3-77.7) and disease control rate (DCR) of 50% (95% CI, 11.8-88.2). Three patients had SD with INCB001158 monotherapy (DCR 50%; 95% CI, 11.8-88.2). No responses or SD were observed with combination therapy.
CONCLUSIONS: Retifanlimab, INCB001158, and their combination had acceptable safety profiles. Promising retifanlimab antitumor activity warrants further investigation in Japanese patients.

BACKGROUND: POD1UM-203, an open-label, multicenter, phase II study, evaluated retifanlimab, a humanized monoclonal antibody targeting programmed cell death protein-1 (PD-1) in patients with selected solid tumors where immune checkpoint inhibitor therapies have previously shown efficacy.
METHODS: Eligible patients (≥18 years) had measurable disease and included unresectable or metastatic melanoma, treatment-naive metastatic non-small-cell lung cancer (NSCLC) with high programmed death-ligand 1 (PD-L1) expression (tumor proportion score ≥50%), cisplatin-ineligible locally advanced/metastatic urothelial carcinoma (UC) with PD-L1 expression (combined positive score ≥10%), or treatment-naive locally advanced/metastatic clear-cell renal cell carcinoma (RCC). Retifanlimab 500 mg was administered intravenously every 4 weeks as a 30-min infusion. The primary endpoint was investigator-assessed overall response rate.
RESULTS: Overall, 121 patients (35 melanoma, 23 NSCLC, 29 UC, 34 RCC) were enrolled and treated. The overall response rate [95% confidence interval (CI)] was 40.0% (23.9-57.9) in the melanoma cohort, 34.8% (16.4-57.3) in the NSCLC cohort, 37.9% (20.7-57.7) in the UC cohort, and 23.5% (10.7-41.2) in the RCC cohort. Median duration of response was 11.5 months (95% CI 2.2-not reached) in the UC cohort, and was not reached in the other cohorts. Retifanlimab safety was consistent with previous experience for PD-(L)1 inhibitors.
CONCLUSIONS: Retifanlimab demonstrated durable antitumor activity in patients with melanoma, NSCLC, UC, or RCC. The efficacy and safety of retifanlimab were as expected for a PD-(L)1 inhibitor. These data support further study of retifanlimab in solid tumors.

BACKGROUND: Retifanlimab is a humanized, hinge-stabilized immunoglobulin G4κ monoclonal antibody against human programmed cell death protein 1 (PD-1). This first-in-human, phase I study assessed the safety and efficacy of retifanlimab in patients with advanced solid tumors and identified optimal dosing.
METHODS: POD1UM-101 was conducted in two parts: (i) dose escalation-evaluated retifanlimab [1 mg/kg every 2 weeks (q2w), 3 or 10 mg/kg q2w or every 4 weeks (q4w)] in patients with relapsed/refractory, unresectable, locally advanced or metastatic solid tumors; (ii) cohort expansion-biomarker-unselected tumor-specific cohorts [endometrial, cervical, sarcoma, non-small-cell lung cancer (NSCLC)] received retifanlimab 3 mg/kg q2w, and tumor-agnostic cohorts received flat dosing [375 mg every 3 weeks (q3w), or 500 and 750 mg q4w]. Primary objectives were safety and tolerability; secondary objective was efficacy in selected tumor types.
RESULTS: Thirty-seven patients were enrolled in dose escalation, 134 in PD-1 therapy-naïve tumor-specific cohort expansion (endometrial, n = 29; cervical, NSCLC, soft tissue sarcoma, each n = 35), and 45 in flat dosing (375 mg q3w, 500 and 750 mg q4w, each n = 15). No dose-limiting toxicities occurred during dose escalation; maximum tolerated dose was not reached and 3-mg/kg q2w expansion dose was selected based on safety and pharmacokinetic data. Immune-related adverse events were experienced by 40 patients (30%) in tumor-specific cohorts (most frequently hypothyroidism, hyperthyroidism, colitis, nephritis) and 6 (13%) in flat dosing (most frequently hypothyroidism, hyperthyroidism). Objective response rate (95% confidence interval) was 14% (4.8 to 30.3), 14% (3.9 to 31.7), 20% (8.4 to 36.9), and 3% (0.1 to 14.9) in advanced NSCLC, endometrial, cervical, and sarcoma tumor-specific cohorts that progressed after multiple prior systemic therapies.
CONCLUSIONS: Retifanlimab demonstrated clinical pharmacology, safety, and antitumor activity consistent with the programmed death (ligand)-1 inhibitor class. POD1UM-101 results support further exploration of retifanlimab as monotherapy and backbone immunotherapy in combination treatments, with recommended doses of 500 mg q4w and 375 mg q3w.

UNASSIGNED: Squamous carcinoma of the anal canal (SCAC) is a human papillomavirus (HPV)-driven cancer with poor prognosis in locally advanced or recurrent settings. Carboplatin-paclitaxel is the preferred first-line regimen for unresectable locally advanced or metastatic SCAC, with the reported median progression-free survival (PFS) and overall survival (OS) of 8.1 and 20.0 months, respectively. Immune checkpoint blockade (ICB) demonstrates improved survival in HPV-driven cervical and head and neck cancers. Retifanlimab (INCMGA00012) is an investigational humanized, hinge-stabilized, immunoglobulin G4κ monoclonal antibody targeting programmed cell death-1 (PD-1), with characteristics common to the ICB class. In POD1UM-202, retifanlimab showed substantial clinical activity and an expected safety profile in patients with advanced SCAC who progressed on platinum-based chemotherapy. Based on these encouraging results, POD1UM-303/InterAACT 2 (NCT04472429), a phase III, double-blind, randomized, multiregional study, investigates the addition of retifanlimab to the standard of care (SOC) carboplatin-paclitaxel in patients with inoperable locally recurrent or metastatic SCAC not previously treated with systemic chemotherapy.
UNASSIGNED: Patients ≥18 years with inoperable locally recurrent or metastatic SCAC, measurable disease per RECIST v1.1, and no prior systemic chemotherapy or PD-(L)1-directed therapy will be enrolled and stratified by PD-L1 expression, region, and extent of disease. Patients with well-controlled human immunodeficiency virus infection are eligible. Planned enrollment is approximately 300 patients worldwide, with a 1:1 randomization to retifanlimab or placebo. Patients will receive up to six induction cycles (24 weeks) of carboplatin (area-under-the-curve 5 on day 1) and paclitaxel (80 mg/m2 on days 1, 8, and 15) every 28 days per SOC. Concurrently, retifanlimab 500 mg or placebo will be administered intravenously in a blinded fashion on day 1 of each 28-day cycle for up to 13 cycles (1 year) in the absence of unacceptable toxicity, disease progression, withdrawal of consent, loss to follow-up, or premature discontinuation. Crossover to open-label retifanlimab will be allowed for patients assigned to placebo upon verification of progression by blinded independent central radiographic review (BICR). The primary study endpoint is PFS per RECIST v1.1 by BICR. Secondary endpoints are OS, objective response rate, duration of response, disease control rate, safety, and retifanlimab pharmacokinetics. The study is currently recruiting.
UNASSIGNED: https://clinicaltrials.gov/ct2/show/NCT04472429; https://clinicaltrialsregister.eu/ctr-search/search?query=2020-000826-24.

BACKGROUND: Locally advanced or metastatic squamous carcinoma of the anal canal (SCAC) has poor prognosis following platinum-based chemotherapy. Retifanlimab (INCMGA00012), a humanized monoclonal antibody targeting programmed death protein-1 (PD-1), demonstrated clinical activity across a range of solid tumors in clinical trials. We present results from POD1UM-202 (NCT03597295), an open-label, single-arm, multicenter, phase II study evaluating retifanlimab in patients with previously treated advanced or metastatic SCAC.
METHODS: Patients ≥18 years of age had measurable disease and had progressed following, or were ineligible for, platinum-based therapy. Retifanlimab 500 mg was administered intravenously every 4 weeks. The primary endpoint was overall response rate (ORR) by independent central review. Secondary endpoints were duration of response (DOR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety.
RESULTS: Overall, 94 patients were enrolled. At a median follow-up of 7.1 months (range, 0.9-19.4 months), ORR was 13.8% [95% confidence interval (CI) 7.6% to 22.5%], with one complete response (1.1%) and 12 partial responses (12.8%). Responses were observed regardless of human immunodeficiency virus or human papillomavirus status, programmed death ligand 1 (PD-L1) expression, or liver metastases. Stable disease was observed in 33 patients (35.1%) for a DCR of 48.9% (95% CI 38.5% to 59.5%). Median DOR was 9.5 months (range, 5.6 months-not estimable). Median (95% CI) PFS and OS were 2.3 (1.9-3.6) and 10.1 (7.9-not estimable) months, respectively. Retifanlimab safety in this population was consistent with previous experience for the PD-(L)1 inhibitor class.
CONCLUSIONS: Retifanlimab demonstrated clinically meaningful and durable antitumor activity, and an acceptable safety profile in patients with previously treated locally advanced or metastatic SCAC who have progressed on or are intolerant to platinum-based chemotherapy.