AstraZeneca's Imfinzi fails to improve survival in head and neck cancer study

AstraZeneca announced Friday that the Phase III KESTREL trial investigating Imfinzi (durvalumab) as a first-line treatment for patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) whose tumours expressed high levels of PD-L1 failed to meet its primary endpoint of improving overall survival (OS).

The study randomised 823 patients with recurrent or metastatic HNSCC to receive first-line treatment with Imfinzi or Imfinzi plus the CTLA-4 inhibitor tremelimumab, versus the standard-of-care EXTREME regimen. The trial's main goal was OS in patients with high PD-L1 expression in the Imfinzi monotherapy arm, while OS in 'all-comer' patients treated with the combination of Imfinzi plus tremelimumab was also tested as a key secondary endpoint.

Imfinzi+ tremelimumab also failed to improve OS

Along with missing the primary objective, AstraZeneca noted that the combination of Imfinzi plus tremelimumab did not indicate an OS benefit in 'all-comer' patients. The company noted that safety and tolerability profiles for Imfinzi as a monotherapy and in combination with tremelimumab were consistent with previous trials. Dave Fredrickson, executive vice president of AstraZeneca's oncology business unit, said "while we are disappointed by these results, insights from the KESTREL Phase III trial will advance our understanding and application of immunotherapy across our clinical development programme."

Analysts at Liberum commented that while Imfinzi "has been a success…and will deliver sales of over $2 billion this year…it increasingly looks boxed in by competing drugs (e.g. Keytruda) that have proven efficacy in a much broader range of indications." The analysts noted that the main indication for the anti-PD-L1 therapy is in unresectable, Stage III non-small-cell lung cancer after chemoradiation therapy, adding that "a further study in this area (PACIFIC-2) is due to read out this year and will need to be a success to ensure [it] retains its place in the market."

Imfinzi generated sales of $533 million in the third quarter of 2020, up 29% year-on-year.

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