GSK's Blenrep hopes take a knock as drug fails trial

GSK has great expectations for its BCMA-directed cancer drug Blenrep, but a failed phase 3 trial in relapsed or refractory multiple myeloma has raised doubts about its prospects – and even the status of its regulatory approval.

In the DREAMM-3 trial, antibody-drug conjugate (ADC) Blenrep (belantamab mafodotin) failed to improve on standard 'PomDex' therapy with pomalidomide/dexamethasone in patients who had previously been treated with at least two rounds of lenalidomide and a proteasome inhibitor therapy.

The median progression-free survival (PFS) was longer for Blenrep compared to PomDex at around 11 months versus seven months, but was not a statistically significant difference, and that was the case also with the overall response rate (ORR) at 41% and 36%, and overall survival at 21.2 months and 21.1 months, respectively.

While Blenrep has been granted accelerated approval by the FDA for multiple myeloma patients who have received at least four prior therapies – including an anti-CD38 monoclonal antibody, a proteasome inhibitor, and an immunomodulatory agent – DREAMM-3 was intended as a confirmatory trial.

That means that, technically, Blenrep hasn't met the criteria for staying on the market, so its 2020 approval is in jeopardy. And the FDA has become much stricter in recent years when it comes to meeting post-marketing requirements for drugs with accelerated approvals.

Needless to say, GSK's chances of moving it up the treatment pathway into earlier-line use have also taken a tumble, along with its hopes of building Blenrep into a £3 billion blockbuster. In its third quarter results, GSK said the drug brought in just £36 million, despite it being the first drug targeting BCMA to reach the market.

Since its launch, other BCMA therapies have reached the market, including most recently Johnson & Johnson's BCMAxCD3 bispecific antibody Tecvayli (teclistamab), as well as CAR-Ts from Bristol-Myers Squibb (Abecma) and J&J (Carvykti).

GSK didn't give much away in its statement on the DREAMM-3 disappointment, other than to say that two other key trials – DREAMM-7 and 8 – will continue as planned and are due to read out next year.

DREAMM-7 is pitting Blenrep against J&J's Darzalex (daratumumab), both in combination with Takeda's proteasome inhibitor Velcade (bortezomib) and dexamethasone, as second-line therapy for relapsed or refractory multiple myeloma.

DREAMM-8, meanwhile, is comparing Blenrep to Velcade on top of PomDex in patients previously treated with a lenalidomide-based regimen, and the ADC is also in earlier-stage testing as a first-line therapy.