GSK's Jemperli follows Merck's Keytruda with FDA nod to target certain tumors regardless of location

Although a tumor-agnostic indication gives Jemperli a larger patient pool, GlaxoSmithKline’s focus for the PD-1 drug is really on earlier lines of treatment that aren’t yet tapped by PD-1/L1 inhibitors and for novel combinations. (Eric Sagonowsky)

GlaxoSmithKline’s PD-1 latecomer Jemperli has scored an FDA go-ahead to expand into a larger cancer field. Once again, it’s following in the footsteps of Merck’s market leader Keytruda, but first-in-class opportunities await down the line. 

The FDA has granted Jemperli an accelerated approval to treat mismatch repair deficient (dMMR) solid tumors that have progressed following prior treatment regardless of their locations in the body, GSK said Tuesday.

The new nod builds on Jemperli’s initial indication, earned in April, which allows the drug only in previously treated dMMR endometrial cancer. In the U.S., an estimated 14% of solid tumors are dMMR, GSK said, citing data from the National Cancer Institute.

Mismatch repair deficiency is a biomarker that has shown improved response to checkpoint inhibitors. Defects in MMR are mostly found in endometrial, colorectal and other gastrointestinal cancers.

GSK earned the expanded label thanks to tumor shrinkage data. As is the case with any conditional nod, GSK needs to verify Jemperli’s benefit in a confirmatory trial for continued approval.

In the phase 1 GARNET trial, Jemperli shrunk tumors in 41.6% of patients across all dMMR tumor types, with the median response lasting 34.7 months. Among the responders, about 95% were still in remission after six months or longer. In the non-endometrial cancer cohort, the response rate was 38.7%.

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In 2017, Keytruda became the first PD-1/L1 inhibitor to score a tumor-agnostic label from the FDA. That approval covered dMMR or microsatellite instability-high disease (MSI-H). The Merck PD-1 drug demonstrated a 39.6% response rate across dMMR/MSI-H tumors in its own early-stage trial. About 78% of patients enjoyed responses of at least six months.

A direct comparison of results from the two trials should be taken with a grain of salt since they included different trial populations.

Although a tumor-agnostic indication gives Jemperli a larger patient pool, GSK’s real focus is on earlier lines of treatment that aren’t yet tapped by PD-1/L1 inhibitors and for novel combinations.

First up, a phase 3 trial dubbed RUBY is testing Jemperli and chemotherapy with or without GSK’s PARP inhibitor Zejula in front-line endometrial cancer. First data from the study are expected later this year, with a potential regulatory filing planned for 2022, GSK’s R&D chief, Hal Barron, M.D., said during an investor event in June.

Another phase 3 trial, dubbed FIRST, is evaluating Jemperli and Zejula in front-line ovarian cancer. Both Jemperli and Zejula joined the British pharma by way of its Tesaro buy.

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Besides those studies, GSK is exploring combinations of Jemperli with anti-cancer treatments targeting TIGIT, TIM-3, LAG-3, STING and PVRIG, Barron said during the event.

If everything plays out, Jemperli could eventually reach £1 billion to £2 billion in peak sales, GSK estimates. That's no match for Keytruda, which registered $4.2 billion sales in the second quarter alone after a 20% year-over-year growth at constant currencies.

Jemperli and Zejula, plus newly approved myeloma drug Blenrep, are part of GSK’s latest push into oncology under CEO Emma Walmsley. Compared with its established presence in infectious diseases, HIV and inflammatory disorders, the company’s cancer portfolio remains relatively small. 

To beef up its oncology pipeline, GSK has turned to dealmaking. In addition to Tesaro, the company has licensed a PVRIG antibody from Surface Oncology. Plus, an anti-CD96 program has emerged from its human genetics data-driven R&D collaboration with 23andMe. Most recently, GSK joined the TIGIT race through a deal with iTeos Therapeutics.