AstraZeneca on Monday reported detailed findings from the Phase III CASPIAN trial, showing that the PD-L1 inhibitor Imfinzi (durvalumab) significantly improved overall survival (OS) in patients with previously-untreated extensive-stage small-cell lung cancer (SCLC), cutting the risk of death by 27%. Results from the study were presented at the World Conference on Lung Cancer (WCLC).
In June, the company said  that the trial met its primary endpoint of OS, with data presented Monday indicating that median OS for patients given Imfinzi plus four cycles of standard-of-care chemotherapy was 13 months compared to 10.3 months for standard-of-care consisting of up to six cycles of chemotherapy and optional prophylactic cranial irradiation. AstraZeneca added that results showed a prolonged OS benefit with an estimated 33.9% of patients alive at 18 months following treatment with Imfinzi plus chemotherapy versus 24.7% for chemotherapy alone.
The drugmaker noted that a significantly higher progression-free survival rate at 12 months was also seen, with rates of 17.5% and 4.7%, respectively. In addition, a 10.3% increase in confirmed ORR was observed while duration of response at 12 months was 22.7% and 6.3%, respectively. "More patients respond, and of those who respond, their responses are more durable," said Dave Fredrickson, AstraZeneca's executive vice president for oncology, adding "that's translating into a significant improvement in overall survival."
Meanwhile, José Baselga, executive vice president of oncology R&D, remarked "we are encouraged to see more than a third of small cell lung cancer patients treated with Imfinzi plus chemotherapy alive at the 18-month landmark, which is remarkable given the aggressive nature of the disease." Baselga added "it is also noteworthy that these results may enable physicians to choose Imfinzi in combination with either cisplatin or carboplatin chemotherapy backbones."
With regards safety, 61.5% of patients experienced a Grade 3 or 4 adverse event with Imfinzi plus standard-of-care, compared to 62.4% with standard-of-care alone, while discontinuation rates due to treatment were 9.4% in both arms.
The CASPIAN study compared Imfinzi in combination with etoposide and either cisplatin or carboplatin chemotherapy, or Imfinzi, the CTLA-4 tremelimumab and chemotherapy versus chemotherapy alone in 537 previously untreated patients with extensive-stage SCLC. The trial will continue to the final analysis of OS for the combination of Imfinzi, tremelimumab and chemotherapy.
In March, the FDA approved  Roche's PD-L1 inhibitor Tecentriq (atezolizumab), in combination with chemotherapy, for the first-line treatment of adults with extensive-stage SCLC, making it the first cancer immunotherapy authorised in this indication. Meanwhile, in June, the agency granted accelerated clearance  to Merck & Co.'s Keytruda (pembrolizumab) as monotherapy for the treatment of patients with metastatic SCLC with disease progression on or after platinum-based chemotherapy and at least one other prior line of therapy.
Commenting on findings from the CASPIAN study, Bloomberg Intelligence analyst Sam Fazeli said the results "not only corroborates Imfinzi's serious challenge to Roche's Tecentriq in this key setting, but also adds support to consensus sales of $3.6 billion in 2023. Detailed data also show potential for better tolerability." Sales of Imfinzi reached $338 million in the second quarter, up from $122 million in the prior year.