Mei, with Bayer and Gilead in its sights, posts pivotal data on blood cancer prospect

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If Mei Pharma’s zandelisib comes to market, it and Kyowa Kirin will co-promote the drug in the U.S. (PDPics/Pixabay)

Mei Pharma’s bid to break into a congested market fought over by Bayer and Gilead has yielded data. The pivotal trial linked zandelisib to a 70% response rate in follicular lymphoma patients but leaves scope to question whether the drug is differentiated enough to crack a competitive space.

In the primary efficacy population of 91 follicular lymphoma patients, Mei reported a 70% objective response rate (ORR) and a 35% complete response rate. The phosphatidylinositol 3-kinase delta (PI3Kδ) inhibitor achieved the response rate in patients who had taken at least two prior systemic therapies, including chemotherapy and an anti-CD20 antibody such as Rituxan, for their blood cancer. 

The data appear competitive—Gilead’s Zydelig posted a 54% ORR at the first interim analysis—and Mei CEO Daniel Gold said they support “plans to continue discussions with the FDA on timing of an accelerated approval submission.” But it is unclear whether the efficacy edge is pronounced enough to secure Mei significant sales. Safety will influence whether that happens, given concerns about the side effects of other PI3Kδ inhibitors.

Ten percent of patients discontinued therapy because of a drug-related adverse event. The most common grade 3 or worse adverse event was diarrhea at 5%. Investigators also saw grade 3 or worse cases of elevated liver enzymes, colitis, mucositis, pneumonitis and rash.

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While four PI3Kδ inhibitors, led by Zydelig, have already come to market, Mei thinks there is an opportunity to improve on the safety and efficacy of the existing products. The class of products suffers from toxicities that led the FDA to impose black box warnings on Zydelig and Secura Bio’s Copiktra and to burden Bayer’s Aliqopa and TG Therapeutics’ Ukoniq with labels that caution about side effects. 

Mei’s belief that zandelisib can improve on the incumbents is underpinned by differences that could result in prolonged target binding and preferential cellular accumulation. With zandelisib having a 28-hour half-life, Mei is pitching zandelisib as suitable for once-daily oral administration and an intermittent dosing schedule designed to minimize immune-related toxicities. 

If zandelisib comes to market, Mei and Kyowa Kirin will co-promote the drug in the U.S. under the terms of a 2020 deal that was worth $100 million upfront and up to $582 million in milestones.