Asco-GI – narrow bile duct win sets Imfinzi on an approval course

Astrazeneca’s Imfinzi could soon add front-line bile duct cancer to its approved uses, though its supporting Topaz-1 study, being presented in full at Asco-GI, has revealed a benefit that might appear underwhelming. In the trial, toplined last October, Imfinzi plus chemo reduced risk of death by 20% versus chemo alone, but median overall survival was just 1.3 months longer than for chemo. However, Dave Fredrickson, Astrazeneca’s head of oncology, told Evaluate Vantage that the medians belied a strong tail in the survival curves, adding: “At two years one in four patients are alive on the Imfinzi/chemo regimen versus one in 10 on chemo alone.” As for biomarkers, he said patients’ PD-L1 status did not seem to be an obvious reason for the late survival benefit. Bile duct cancer patients have seen US approvals of Incyte’s Pemazyre and Bridgebio’s Truseltiq, both in FGFR2-mutant disease, and Agios’s Tibsovo, but these have all been second line. Whether follow-on use of any of these might have affected the Topaz-1 data has yet to be analysed. Either way, Topaz-1 marks the first win for IO here, and 2023 should see data from front-line studies of Merck & Co’s Keytruda (Keynote-966) and Roche’s Tecentriq (Imbrave-151).

Summary of Topaz-1 data
  Imfinzi + chemo Chemo
mOS (primary endpoint) 12.8mth 11.5mth
Stats HR=0.80 (p=0.021)
mPFS (secondary endpoint) 7.2mth 5.7mth
Stats HR=0.75 (p=0.001)
ORR (secondary endpoint) 26.7% 18.7%
Grade 3/4 AEs 75.7% 77.8%
Treatment-related deaths 2/341 1/344
Source: Astrazeneca & Asco-GI.

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