Black Diamond Therapeutics Stock Plunges On Safety Signals In Solid Tumor Study Of BDTX-189

Black Diamond Therapeutics Inc BDTX reported initial data from the Phase 1 dose-escalation portion of the Phase 1/2 MasterKey-01 trial evaluating BDTX-189 in patients with advanced solid tumors.
The data will be presented at the American Society of Clinical Oncology Annual Meeting.
Till the cut-off date of April 2, 55 patients from twice-daily regimen were dosed. In a heavily pre-treated patient population, evidence of anti-cancer activity was observed.
One confirmed partial response was observed in a lung cancer patient with EGFR Exon 20 mutation, who had previously responded and then progressed on poziotinib (at the data cut-off, 53% tumor regression observed).
All three patients with NSCLC HER2 Exon 20 demonstrated stable disease.
In the HER2-amplification cohort (n=6), one confirmed partial response (PR), with 90% tumor reduction, one unconfirmed PR (NSCLC), two patients with stable disease (ovarian and pancreatic), and two patients with progressive disease were observed.
On the safety front, gastrointestinal events were the most common drug-related adverse events, low grade and manageable after medical intervention.
50% of the patients reported diarrhea & nausea, followed by vomiting in 30%. 13% also reported skin disorders.
The company remains on track to initiate the potentially pivotal Phase 2 portion of the MasterKey-01 trial in the second half of 2021.
Price Action: BDTX shares are down 29.2% at $15.74 during the premarket session on the last check Thursday.