Pfizer's PF-05280586 Shows Equivalence to Reference Rituximab in Comparative Study

Pfizer announced today that PF-05280586, the company’s proposed biosimilar to reference rituximab (Rituxan, MabThera), has been shown to be equivalent to the reference in overall response rate (ORR) for the first-line treatment of patients with CD20-positive, low tumor burden follicular lymphoma.

The positive top-line results were reported from the phase 3 REFLECTIONS B3281006 study, a randomized, double-blind clinical trial evaluating the efficacy, safety, pharmacokinetics (PK), and immunogenicity of PF-05280586 versus the EU-approved MabThera.

REFLECTIONS B3281006 had an estimated enrollment of 394 adult participants and began in September 2014. It is expected to be completed later in 2018. The primary endpoint, ORR, is defined according to the revised response criteria for malignant lymphoma (time frame, week 26). Secondary outcome measures include time to treatment failure, progression-free survival, complete remission rate, duration of response, overall survival, incidence of anti-drug antibodies, and safety associated with immune response.

“These results reinforce the potential of our proposed rituximab biosimilar in providing a safe and effective treatment option for patients,” said Amrit Ray, MD, global president, Pfizer Essential Health Research and Development. “We are delivering on our commitment to advancing high-quality medicines for the millions of patients with cancer around the world today and in the future,” added Ray.

Pfizer has also investigated the proposed biosimilar for inflammatory indications. An earlier phase 1 clinical trial of PF-05280586 demonstrated pharmacokinetic similarity to US-licensed Rituxan and MabThera in 220 patients with active rheumatoid arthritis (RA) with inadequate response to 1 or more anti—tumor necrosis factor (anti-TNF) therapies. The researchers reported comparable pharmacodynamic responses as well as safety and immunogenicity profiles.

Another clinical trial of PF-05280586 in 214 patients with RA who had an inadequate response to anti-TNF drugs found no clinically meaningful differences in Disease Activity Score in 28 Joints (DAS28) or American College of Rheumatology (ACR) improvement criteria between the proposed biosimilar and the 2 reference drugs.

The complete results of the REFLECTIONS B3281006 trial will be submitted for presentation at a future medical conference or publication in a summary format, according to Pfizer.

Pfizer has 7 distinct biosimilar molecules in mid- to late-stage development, with 3 of these in oncology, as well as several others in early-stage development.