Merck & Co. Inc. said its blockbuster drug Keytruda was approved in Japan as an initial treatment for patients with either a specific head and neck cancer or a kidney cancer subtype.

Japan's Pharmaceuticals and Medical Devices Agency approved Keytruda, or pembrolizumab, as a first-line treatment for patients whose advanced renal cell carcinoma, a common type of kidney cancer, has spread or cannot be surgically removed.

The approval is based on a late-stage study called Keynote-426, which evaluated Keytruda in combination with Pfizer Inc.'s Inlyta as first-line therapy for patients with renal cell carcinoma that has grown outside the kidney or has spread to other parts of the body.

The study showed that the drug combination significantly improved overall survival as well as boosted the amount of time the patient lived without the disease worsening — a measure known as progression-free survival.

The Kenilworth, N.J.-based drugmaker's medicine was also approved in combination with chemotherapy as an initial treatment for patients with recurring or distant head and neck squamous cell carcinoma, or HNSCC, that has spread beyond the origin site.

Additionally, Keytruda was approved in Japan as a standalone treatment for the same indication, Merck said in a Dec. 20 press release.

The two approvals are based on a phase 3 study, called Keynote-048, which found that Keytruda with or without chemotherapy helped patients with HNSCC that had recurred or spread to other parts of the body live longer than the standard of care.

It is estimated that about 24,000 people in Japan were diagnosed with kidney cancer in 2018, and about 22,000 new cases of head and neck cancer came up that year.