Quark, Pfizer initiate phase 2 trial of DME treatment

FREMONT, Calif. — Pfizer has initiated patient dosing for a prospective, randomized, dose-ranging phase 2 clinical trial evaluating a novel siRNA drug candidate in patients with diabetic macular edema, according to a press release from Quark Pharmaceuticals, a development partner of Pfizer.

The drug, PF-4523655, is a synthetic siRNA molecule designed to inhibit the expression of RTP801, a gene involved in abnormal blood vessel development and leakage in the eye, the release said.

The multinational clinical trial is evaluating the safety and efficacy of PF-4523655 compared with laser therapy in 160 patients with DME. Eligible patients will be randomly assigned to receive intravitreal injections of one of three dose levels of PF-04523655 or laser treatment. The investigators will assess therapeutic effect based on visual acuity and morphological examinations of the retina conducted over 36 months of follow-up.

Under the terms of the companies' global licensing agreement, Pfizer owns exclusive development rights to siRNA-mediated therapies that inhibit RTP801 for ophthalmic and non-ophthalmic indications, and Quark is entitled to receive sales- and development-based milestone payments. The initiation of the trial prompts Pfizer to pay Quark a milestone payment, of which Quark will tender a small percentage to Silence Therapeutics and Alnylam as technology license milestone payments, according to the release.

Results from a phase 1/2 trial of PF-4523655 completed by Quark on Pfizer's behalf found that the drug was safe and well-tolerated in patients with wet age-related macular degeneration who failed to respond to currently approved therapies. Consequently, Quark and Pfizer are currently considering an additional phase 2 trial of PF-4523655 in wet AMD patients.