GSK plc (LON: GSK), the London-listed drugmaker, released two sets of cancer trial data from the ESMO Congress in Madrid, one on Friday and one on Saturday. The Jemperli results came out on Saturday, after markets had closed, so today’s session is the first reaction to them.
Friday’s release updated phase I BEHOLD-1 data for mocertatug rezetecan (Mo-Rez), an investigational B7-H4-targeted antibody-drug conjugate, in platinum-resistant ovarian cancer, with more than 13 months of follow-up. At the 5.8 mg/kg dose selected for phase III, 62% of 45 patients (28) had a confirmed response. Median response lasted 12.2 months and median progression-free survival was 11.1 months.
Grade 3 or worse treatment-related adverse events hit 71% of those patients (32 of 45), predominantly haematologic, and 2% stopped treatment because of them. Five pivotal phase III studies across ovarian and endometrial cancers are under way. Hesham Abdullah, SVP, Global Head Oncology R&D at GSK, said:
Current treatment options for patients with platinum-resistant ovarian cancer are limited and achieving durable responses remains a challenge.
Hesham Abdullah, GSK
Saturday’s release covered interim phase II AZUR-1 results for Jemperli (dostarlimab) alone in stage II/III locally advanced rectal cancer with MSI-H/dMMR tumours, a subtype making up 5% to 10% of rectal cancers. In an exploratory analysis, 76% of evaluable patients (110 of 144) had a complete response, and no responders had a recurrence after median follow-up of more than two years.
The caveat is the primary endpoint: sustained clinical complete response at 12 months by independent central review is still maturing, at 47% (54 of 116), with another 38 patients not yet at 12 months. GSK said the trial met its primary objective, and the data supported the recent US approval. Serious adverse reactions occurred in 20% of patients.
GSK shares closed Friday at 1894p, down 1.04% after a 2.46% rise on Thursday. That left them 16.5% below the 2268p closing high of the 18th of February, 16.9% above the 52-week closing low of 1620p, and 15.0% higher than a year ago.
The three-month picture is flat, down 0.60%, but the path was uneven. The close fell to 1735.5p on the 8th of October, then rose 3.6% and 2.9% on the 14th and 15th. In New York, GSK closed Friday at $50.75, down 0.90%.
Regulatory reviews of the rectal cancer use are continuing in participating countries through Project Orbis, and GSK said endometrial cancer data for Mo-Rez will be presented in future.