Jounce Therapeutics, Inc. announced that patients from the INNATE Phase 2 trial in the ovarian cancer combination cohort with platinum resistant ovarian cancer are experiencing deep and durable responses based on a pre-planned informal data review. The INNATE trial evaluates JTX-8064 as a monotherapy and in combination with the PD-1 inhibitor pimivalimab in patients with advanced solid tumors. JTX-8064, is a humanized IgG4 monoclonal antibody designed to specifically bind to the macrophage receptor Leukocyte Immunoglobulin Like Receptor B2 (LILRB2/ILT4), inhibiting LILRB2 binding with its obligations which may result in reprogramming immune-suppressive macrophages to enhance anti-tumor immunity.

A data review was conducted on March 15, 2023 to assess the potential to achieve proof-of-concept (POC) in the ovarian cancer combination cohort of the INNATE trial. In this cohort, 35 patients with third- and fourth-line platinum resistant ovarian cancer were treated with JTX-8064 and Jounce's PD-1 inhibitor, pimivalimab. There were five RECIST 1.1 responders, four of which are confirmed, with all five patients remaining on study for over six months with continued tumor reduction over time.

The remaining 30 patients have discontinued treatment. Upon confirmation of a fifth confirmed partial response (PR), the ovarian combination cohort would meet Jounce internal criteria for POC, based on a statistically meaningful improvement over the benchmark of pembrolizumab alone in the analogous setting. In patients with one to six prior lines of therapy for ovarian cancer, pembrolizumab monotherapy demonstrated a response rate of 8.5%, with duration of response of 10.2 months.

Two of the five responders in INNATE have a PD-L1 score of zero, indicating a low likelihood of response to a PD-1 inhibitor. The combination was well tolerated with <10% of patients reporting Grade 3 or greater related adverse events. Enrollment has been completed in all cohorts in the INNATE trial.

In addition to the patients with ovarian cancer, both durable responses and stable disease have occurred in patients with renal cell carcinoma, biliary tract cancer, and first-line and second/third-line head and neck squamous cell carcinoma, but the ovarian data is the most encouraging with potential to achieve pre-determined POC criteria. As previously announced, Jounce is seeking to partner JTX-8064. Jounce continues to believe a company with additional resources and a longer value creation timeline could potentially advance this program for the benefit of cancer patients.