The FDA has granted approval to Merck's Keytruda (pembrolizumab) in combination with pemetrexed and platinum chemotherapy for the first-line treatment of adult patients with unresectable advanced or metastatic malignant pleural mesothelioma (MPM). This decision marks a significant advancement in the treatment landscape for this rare and aggressive cancer, which originates in the lining of the lungs and chest.
The approval is based on data from the Phase 2/3 KEYNOTE-483 trial, a randomized, open-label study involving 440 patients with unresectable advanced or metastatic MPM who had not previously received systemic therapy for advanced disease. The trial compared the efficacy and safety of Keytruda plus chemotherapy against chemotherapy alone.
KEYNOTE-483 Trial Results
Results from the KEYNOTE-483 trial demonstrated a statistically significant improvement in overall survival (OS) for patients treated with Keytruda in combination with chemotherapy. The median OS was 17.3 months (95% CI, 14.4-21.3) for the Keytruda arm, compared to 16.1 months (95% CI, 13.1-18.2) for the chemotherapy arm (HR, 0.79; 95% CI, 0.64-0.98; p=0.0162). This represents a 21% reduction in the risk of death.
In addition to the improvement in OS, the Keytruda regimen also showed significant benefits in progression-free survival (PFS) and overall response rate (ORR). The median PFS was 7.1 months in both arms (HR, 0.80; 95% CI, 0.65-0.99; P = .0194). The confirmed ORR was 52% (95% CI, 45.5%-59.0%) with pembrolizumab-based treatment vs 29% (95% CI, 23.0%-35.4%) in the chemotherapy-alone arm.
Safety Profile
The safety profile of Keytruda in combination with pemetrexed and platinum chemotherapy was generally consistent with what had been established in previous studies. Common adverse reactions included fatigue, nausea, constipation, diarrhea, decreased appetite, rash, vomiting, cough, dyspnea, pyrexia, alopecia, peripheral neuropathy, mucosal inflammation, stomatitis, headache, weight loss, abdominal pain, arthralgia, myalgia, insomnia, palmar-plantar erythrodysesthesia, urinary tract infection, and hypothyroidism.
Implications for MPM Treatment
This approval marks a significant milestone in the treatment of MPM, a rare and aggressive cancer often associated with asbestos exposure. With limited treatment options available, the Keytruda regimen offers a new first-line therapy that has demonstrated improved survival outcomes. According to the American Cancer Society, approximately 3,000 new cases of mesothelioma are diagnosed each year in the United States, with MPM accounting for about 75% of all cases. The five-year survival rate for MPM is generally poor, underscoring the need for more effective treatments.
Gregory Lubiniecki, vice president of oncology clinical research at Merck Research Laboratories, stated, "We’re pleased to offer a new first-line treatment option for adult patients with unresectable advanced or metastatic malignant pleural mesothelioma, a disease where prognoses are generally poor. This milestone underscores our commitment to advancing research for patients with difficult-to-treat tumors."
Dosing and Administration
The recommended dose of Keytruda is 200 mg every 3 weeks or 400 mg every 6 weeks, administered intravenously until disease progression or unacceptable toxicity, for up to 2 years. It is given in combination with pemetrexed and platinum-based chemotherapy.
