A phase 1/2 study of favezelimab in combination with pembrolizumab for anti–PD-1–naive relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL): An updated analysis.

7055 Background: PD-1 inhibitors such as pembrolizumab are an important treatment option for patients (pts) with R/R cHL, but treatment failure remains a significant challenge. Dual immune checkpoint blockade with a PD-1 inhibitor and a lymphocyte-activation gene 3 (LAG-3) inhibitor shows promise as a treatment option for R/R cHL. In a multicohort phase 1/2 study (NCT03598608) evaluating the anti–LAG-3 monoclonal antibody favezelimab in combination with pembrolizumab for R/R hematologic malignancies, pembrolizumab plus favezelimab demonstrated sustained antitumor activity and acceptable safety in the cohort of pts with anti–PD-1–naive R/R cHL (cohort 1). We present updated results from this cohort after additional follow-up. Methods: Eligible pts were aged ≥18 years with R/R cHL; prior treatment with or ineligibility for autologous stem cell transplantation or no response to salvage chemotherapy; no prior PD-1 inhibitor; and an ECOG PS of 0 or 1. The study comprised a safety lead-in (pembrolizumab 200 mg IV Q3W plus favezelimab 200-mg starting dose, then dose escalation to 800 mg IV Q3W using a modified toxicity probability interval method) and a dose expansion phase (pembrolizumab 200 mg Q3W plus favezelimab at the established recommended phase 2 dose of 800 mg Q3W for up to 35 cycles). Primary end point was safety. Objective response rate (ORR) per IWG 2007 criteria by investigator review was a secondary end point. Duration of response (DOR) and progression-free survival (PFS) per IWG 2007 criteria by investigator review and overall survival (OS) were exploratory. Results: Cohort 1 enrolled 30 pts. The median time from first dose to data cutoff (August 15, 2023) was 36.9 months (range, 29.4-48.6). Treatment-related adverse events (AEs) occurred in 27 pts (90%), of which the most common (≥20%) were hypothyroidism (27%), infusion-related reaction (23%), and fatigue (20%). Grade 3 or 4 treatment-related AEs occurred in 7 pts (23%). Five pts (17%) discontinued treatment due to treatment-related AEs. No deaths due to treatment-related AEs were reported. AEs of clinical interest occurred in 20 pts (67%); 3 pts (10%) had grade 3 events (colitis, pneumonitis, severe skin reaction) and 1 pt (3%) had a grade 4 event (hepatitis). The ORR was 83% (n = 25; 95% CI, 65-94); 11 pts (37%) had a complete response and 14 (47%) had a partial response. Median DOR was 17.0 months (range, 2.6-30.5), and an estimated 47% of responders remained in response at 24 months. Median PFS was 19.4 months (95% CI, 9.5-28.5), and the 24-month PFS rate was 46%. Median OS was not reached (NR; 95% CI, NR-NR), and the 24-month OS rate was 93%. Conclusions: With additional follow-up, favezelimab plus pembrolizumab continued to demonstrate sustained antitumor activity and manageable safety in pts with anti–PD-1–naive R/R cHL. Further studies to investigate this combination are warranted. Clinical trial information: NCT03598608 .