After an apparent accidental early release, Pfizer has revealed phase 1 data showing its investigational candidate, alongside Xtandi, reduced prostate cancer progression by 49%.
The data, centering an investigational small molecule EZH2 inhibitor called mevrometostat, were initially scheduled for a Feb. 13 presentation at the ASCO Genitourinary Cancers Symposium in San Francisco. However, the abstract was posted early after a portion of it was shared on the ASCO-GU daily news site.
The open-label trial enrolled 81 patients with metastatic castration-resistant prostate cancer (mCRPC) who had received prior treatment. For the 41 patients receiving both mevrometostat and Xtandi (enzalutamide), median radiographic progression-free survival was 14.3 months. The result compared with 6.2 months for the 40 patients who received only Xtandi.
For the 15 patients who received the investigational combo and had measurable disease at baseline, the overall response (OR) rate was 26.7%. This is compared to a 14.3% OR rate for the 14 eligible patients on enzalutamide.
Grade 3 or higher treatment-emergent adverse events (TEAEs) occurred in 53.7% of patients receiving the combo, with the most common of these events being diarrhea, neutropenia and sepsis. In the monotherapy cohort, 42.5% of patients experienced TEAEs.
No treatment-related deaths were reported as of the September 2024 cutoff.
Researchers deemed the combo as improving outcomes and having a manageable safety profile, according to the abstract, which was drafted by Pfizer's generative AI tool “MAIA.”
The results come from an ongoing dose-escalation and expanded-cohort study that is also testing out the combo among patients with advanced small cell lung cancer and follicular lymphoma.
Pfizer has already launched two phase 3 trials to assess mevrometostat and enzalutamide for androgen receptor pathway inhibitor-naïve patients with mCRPC and for patients with mCRPC who have previously received Johnson & Johnson’s Zytiga.
Meanwhile, Pfizer also announced a new deal with Boston biotech Alloy Therapeutics aimed at developing a new platform that can discover antibodies to tackle targets that are difficult to access with existing tech.
Alloy will receive an upfront payment of an undisclosed amount and will also have the chance to collect certain biobucks payments, according to a Feb. 11 release.
Alloy’s ATX-Gx platform is based on a collection of fully humanized transgenic mice and is being used by more than 170 partners, according to the biotech.
The deal expands on an existing partnership between Pfizer and Alloy in which the pair worked together on a range of antibody discovery efforts and leveraged the biotech’s ATX-CLC platform. The science is made to generate human antibodies using a single light chain sequence, according to Alloy.