ASCO 2026 preview – Black Diamond tries to catch up with Arrivent

With the battle of next-generation EGFR inhibitors turning to first-line lung cancer, Black Diamond has tried to catch up to Arrivent by detailing the first progression-free survival data for its lead project, silevertinib.

The median PFS number, 15.2 months, as disclosed on an investor call after market close on Thursday, is just short of the 16.0 months Arrivent revealed for its rival, firmonertinib, at last year’s World Lung conference. Whether the two datasets are comparable is one consideration, but investors got a nasty surprise with revelation of silevertinib’s toxicity profile.

Black Diamond said grade 3 treatment-related adverse events for the dose tested, 200mg, were experienced by 60% of the 43 patients involved; this fell to 28% on dose reduction. So concerning is this profile that the group is proposing to take 150mg forward into a registrational trial.

Of course whether it can do this will be up to the FDA. More importantly, investors now have to bear in mind that silevertinib’s efficacy is likely to fall further on lower dosing. Black Diamond, which carries a seemingly undemanding market cap of $200m, saw its stock open down 20% on Friday.

ASCO prelude

The company arranged the investor call as a prelude to ASCO, where the silevertinib data will be presented in full, but whose abstract, also unveiled after market on Thursday, revealed nothing new.

The setting for this phase 1 silevertinib trial is first-line NSCLC with non-classical (including PACC, or P-loop alpha-c helix compressing) mutations, Black Diamond having earlier abandoned the relapsed setting. The group reckons non-classical mutations are present in a quarter of the treatment-naive NSCLC population, with PACC accounting for less than half of these.

Such patients have no approved treatments, though AstraZeneca’s Tagrisso and Boehringer Ingelheim’s Gilotrif are sometimes given off-label. Last December Black Diamond reported a promising 60% ORR in 43 non-classical mutation NSCLC patients, including 56% in those with PACC mutations, and these numbers were unchanged in the ASCO abstract. 

The mPFS number of 15.2 months was new, with Black Diamond claiming that a 40% increase above earlier-generation drugs would be “practice changing”. To back up this claim it cited anecdotal mPFS numbers of 10 and eight months for Gilotrif and Tagrisso respectively.

So far so good, but the fact remains that Arrivent has already touted 16.0 months of mPFS from a phase 1 firmonertinib trial in first-line PACC-mutant NSCLC.

Cross-trial ph1 comparison in 1st-line NSCLC with non-classical mutations

Note: 150mg, not 200mg, is to be taken forward. Source: OncologyPipeline.

On the investor call Black Diamond insisted that the datasets weren’t comparable, since Arrivent’s came largely from Asia, featured a more limited mutation profile, and had meaningfully fewer patients with CNS disease.

Firmonertinib’s 16-month mPFS is a mature number whereas median duration of response for silevertinib has yet to be reached, so “our PFS has a decent chance of getting stronger” with longer follow-up, Black Diamond claimed. This could yet happen, but investors now have to guess how well a lower 150mg silevertinib dose will perform.

It seems clear that 200mg isn’t viable, given the 88% rate of dose interruption, 84% dose reduction, and 14% of patients discontinuing owing to adverse events, detailed by Black Diamond for the 200mg dose.

Safety and efficacy data support 150mg as the dose for pivotal development, the company told investors. A registrational study has yet to be discussed with the FDA, and in any case Black Diamond needs to secure more cash to be able actually to run one.