Arcus Biosciences announced that quemliclustat, an investigational small-molecule CD73 inhibitor, has been granted orphan drug designation by the U.S. Food and Drug Administration for the treatment of pancreatic cancer. The designation recognizes the critical need for new therapeutic options in a disease with the highest mortality rate among all major cancers and limited treatment advances over the past three decades.
CD73 Inhibition Mechanism and Clinical Rationale
Quemliclustat is a potent and selective small molecule CD73 inhibitor being co-developed in collaboration with Gilead Sciences. CD73 serves as the primary enzymatic producer of immunosuppressive adenosine in the tumor microenvironment, and high CD73 expression is associated with significantly poorer prognosis in several tumor types. By inhibiting this pathway, quemliclustat aims to reduce immunosuppression and enhance anti-tumor immune responses.
Promising Phase 1 Results Drive Development Forward
In January 2024, Arcus presented results from the Phase 1 ARC-8 study, which demonstrated no new safety signals and achieved a median overall survival of 15.7 months in a pooled analysis of all patients treated with 100mg quemliclustat-based regimens. Notably, the median overall survival exceeded historical benchmark data for chemotherapy alone, including patients with liver metastasis, which accounts for more than half of all pancreatic cancers.
Phase 3 PRISM-1 Study Design and Objectives
Based on the encouraging ARC-8 results, Arcus has initiated PRISM-1, a registrational Phase 3 study designed to evaluate quemliclustat plus gemcitabine/nab-paclitaxel chemotherapy versus gemcitabine/nab-paclitaxel chemotherapy alone. The global, randomized, double-blind, placebo-controlled, multi-center study will enroll approximately 610 patients with treatment-naïve metastatic pancreatic ductal adenocarcinoma.
Participants will be randomized in a 2:1 ratio between the quemliclustat plus gemcitabine/nab-paclitaxel chemotherapy arm and the gemcitabine/nab-paclitaxel chemotherapy plus placebo arm. The primary endpoint is overall survival, while secondary endpoints include progression-free survival, objective response rate, duration of response, disease control rate, and safety. The study is expected to be fully enrolled this year.
Regulatory Benefits and Market Impact
The orphan drug designation qualifies Arcus for several regulatory incentives, including tax credits for qualified clinical trials, exemption from user fees including New Drug Application fees, and potential seven years of market exclusivity after approval. Chief Medical Officer Richard Markus emphasized that "the orphan drug designation indicates the importance of developing new treatment options for rare diseases like pancreatic cancer, which has the highest mortality rate of all major cancers, and which has seen few treatment advancements over the past 30 years."
Orphan drug designation is specifically intended to support the development and evaluation of new treatments for rare diseases affecting fewer than 200,000 people in the United States, highlighting the significant unmet medical need in pancreatic cancer treatment.
