A first-in-human phase I study of the PD-1 inhibitor, retifanlimab (INCMGA00012), in patients with advanced solid tumors (POD1UM-101)

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.

PATIENTS AND 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.

Long-term survival of patients (pts) with advanced melanoma treated with ipilimumab with or without dacarbazine

9038

Background: Ipilimumab is a fully human monoclonal antibody targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4). Here, we report updated survival of pts with advanced melanoma treated with ipilimumab in 2 completed studies. Methods: Seventy-two chemotherapy-naïve pts were randomized to receive 3 mg/kg ipilimumab every 4 weeks (Q4W) × 4 alone or with ≤6 × 5-day courses of DTIC 250 mg/m2/day (ipilimumab, n = 37; ipilimumab + DTIC, n = 35) in the multicenter, open- label Phase II study MDX010–08 (Sep 2002-Aug 2004)(Hersh E et al. J Clin Oncol 26: 2008 (May 20 suppl; abstr 9022)). In the phase I/II dose-ranging study MDX010–15, 23 pts were treated with 10 mg/kg ipilimumab every 3 weeks (Q3W) × 4 (induction) (Jun 2004- Jul 2006) (Urba W et al. J Clin Oncol 26: 2008 (May 20 suppl; abstr 3018)). No maintenance ipilimumab was administered in either study. Long-term survival was determined under a follow-up protocol (MDX010–28) from May 2007-Jan 2008. Results: Long-term data are available for 62 pts for MDX010–08 and 22 pts for MDX010–15. For MDX010–08, the median follow-up was 4.3 years (range, 4.0–4.7 years); it was 2.2 years (range, 2.0–2.4 years) for MDX010–15. Survival rates are reported in the Table . Conclusions: Ipilimumab monotherapy, administered at 3 mg/kg and without maintenance dosing, resulted in survival rates better than those observed with historical controls (Korn EJ et al. J Clin Oncol 26:527–34; 2008). Adding DTIC to ipilimumab did not suppress the effect of ipilimumab (as might have been predicted), but enhanced it still further. Consistent with previously reported response data showing that 10 mg/kg is the recommended dose (study CA184022) (Hamid O et al. J Clin Oncol 26: 2008 (May 20 suppl; abstr 9025)), there was a trend toward better survival with the higher dose (eg, a 2-year survival rate of 36% vs. 22% for 10 mg/kg vs. 3 mg/kg).

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Phase I clinical results of an APC-targeted hCGβ vaccine (CDX-1307) with TLR agonists

3006

Background: Effective immunization requires efficient antigen delivery to antigen presenting cells (APCs). Antigens attached to the human antibody B11, targeting mannose receptors on APCs, have been shown to be processed and presented efficiently, and generate robust immune responses when combined with toll-like receptor (TLR) agonists. The CDX-1307 vaccine is composed of B11 fused with hCGβ, a tumor antigen correlated with advanced stage of disease and poor prognosis in a number of common epithelial cancers, but reported at variable rates of expression. Methods: Two phase I studies investigate intradermal (id) vs. systemic (iv) administration of CDX-1307. Patients with advanced epithelial cancers known to frequently express hCGβ receive 4 biweekly vaccinations of CDX-1307, alone or in combination with immunostimulants including GM-CSF (GM), the TLR3 agonist Poly-ICLC, and the TLR7/8 agonist resiquimod. Results: Dose-escalation is complete. In the id study, 37 patients received CDX-1307 at doses of 0.3, 1.0, and 2.5 mg, then 2.5 mg + GM, 2.5 mg + GM + Poly-ICLC, and 2.5 mg + GM + resiquimod. 2.5 mg + GM + Poly-ICLC + resiquimod is planned. In the iv study, 24 patients were treated at 1, 3, 10, and 30 mg, as well as 10 mg + GM and 30 mg + GM. 30 mg + GM + Poly-ICLC is enrolling. Treatment-related toxicities were generally mild to moderate with no dose-limiting toxicities, most frequently injection site reactions and fatigue in the id study, and fatigue, myalgia, and flu-like illness in the iv study. Humoral responses to hCGβ were increased in 56% of the analyzed patients receiving adjuvants. Serum hCGβ was frequently elevated at study entry or during treatment (males = 88%, females = 53%, pancreatic = 89%, colorectal = 78%, breast = 47%). hCGβ decreases were seen in some patients with immune responses. To date, a significant mixed response was seen in one patient with pancreatic cancer (id), while stable disease has been seen in 4 patients (2 with breast cancer = 25, 27 weeks and 2 with colorectal cancer = 9+ weeks). Conclusions: CDX-1307 is well tolerated and results in immune responses that are enhanced by immunostimulants. Elevated hCGβ was detected at a higher than expected frequency in these tumors.

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Phase II experience with MDX-1106 (Ono-4538), an anti-PD-1 monoclonal antibody, in patients with selected refractory or relapsed malignancies

3018

Background: Programmed death-1 (PD-1), an inhibitory receptor expressed on activated T cells, may suppress antitumor immunity. This expansion cohort in a phase I/II trial of MDX-1106, a fully human IgG4 antibody blocking PD-1, sought to further evaluate the safety and activity of the 10 mg/kg dose. Other objectives included evaluation of pharmacokinetics (PK) and immunological effects. Methods: Patients (pts) with treatment refractory metastatic non-small cell lung cancer (NSCLC), renal cell carcinoma (RCC), colon cancer (CC), melanoma (MEL), or prostate cancer (CRPC), and no history of autoimmune disease received a single infusion of MDX-1106 at 10 mg/kg. Disease status was evaluated at week (wk) 8 by RECIST criteria. Pts with stable disease or lesional responses could receive additional MDX-1106 at wks 12 and 16. Those with PR/CR were observed without retreatment. Results: 21 pts (5 CC, 2 NSCLC, 8 MEL, 5 HRPC, 1 RCC) were treated from 10/07 to present, and 6 were retreated. No MDX-1106 related SAEs occurred. One pt developed arthritic symptoms requiring treatment, and 2 pts had asymptomatic TSH elevation. One pt with RCC had a PR after 3 doses, lasting 5+ months (mo). Lesional regressions (“mixed response”) were seen in 2 MEL pts; to date, one has received 7 doses of MDX-1106 over 15 mo without serious toxicity. Biopsy of a regressing MEL lymph node metastasis showed a moderately increased and selective CD8+ T cell infiltrate post treatment. The median serum t 1/2 of MDX-1106 was 20.6 days, which was roughly 50% longer than observed for lower doses. There was no evidence of immunogenicity based on HAHA development. Interestingly, in contrast to PK results, flow cytometric analysis demonstrated sustained occupancy of 60–80% PD-1 molecules on T cells for at least 3 mo following a single dose. Analyses of circulating lymphocyte subsets and tumor B7-H1 expression are in progress. Conclusions: Intermittent dosing of MDX-1106 at 10 mg/kg demonstrated clinical activity against RCC and MEL without serious toxicity. Therapy with MDX-1106 to enhance endogenous antitumor immunity, either alone or combined with other immunological therapies, warrants further study.

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