GSK flashes positive data for Tesaro drug that could become 7th approved PD-(L)1
A dark horse asset from GlaxoSmithKline’s $5.1 billion buyout of Tesaro is out with its first batch of data in over a year — promising data that could line up the British drugmaker for the 7th FDA approved PD-1 drug, although it’s not clear when.
When GSK purchased the Waltham-based cancer biotech in December of 2018, conversation focused rightly on Zejula, the already-approved PARP inhibitor, and whether the new executive crew of Hal Barron and Emma Walmsley were right in their assertion that the drug could both rival AstraZeneca’s Lynparza and have utility in more than just ovarian cancer. But Tesaro also brought a couple of other clinical stage assets. Chief among them: a PD-1 inhibitor called dostarlimab.
GSK first released data for dostarlimab four months after the buyout. Today they’re back with another set that, while not overwhelming, helps confirm some of the promise of the initial round. In 71 patients with recurrent or advanced mismatch repair-deficient (dMMR) endometrial cancer that progressed on or after chemotherapy, the drug led to a 42% overall response rate and a 58% disease control rate. That broke down into 13% complete response rate and a 30% partial response rate.
The data were for one cohort of the larger Phase I/II GARNET trial that first read out last year. Four others are also underway and still enrolling for patients with different types of the endometrial cancer, which GSK cites as the most common gynaecologic malignancy.
When GSK released the first data in March 2019, the drugmaker said they would submit a BLA for second-line endometrial cancer to the FDA by the end of the year, and they quietly disclosed that they had done so in their 2019 full-year report. Although there’s still no word on when that application was submitted, GSK said in the report that anticipated approval is expected in the second half of 2020.
As with their PARP inhibitor Zejula, dostarlimab would enter a crowded market — what has become, in fact, one of the most crowded markets in oncology, with six different PD-1/L1 therapies on the market and a clear giant in the field in Merck’s Keytruda. Few, though, are approved for endometrial cancers. An approval could help some of those patients, and also go a ways toward justifying Tesaro’s cost and signaling GSK’s return to oncology.