Merck, known as MSD outside the United States and Canada, announced that Japan’s Ministry of Health, Labour and Welfare (MHLW) has approved Keytruda Qlex (pembrolizumab and berahyaluronidase alfa-pmph) injection for subcutaneous use across all indications approved in Japan for Keytruda (pembrolizumab), the company’s anti-PD-1 therapy. In Japan, Keyject is the planned trademark for Keytruda Qlex for subcutaneous injection.

Keyject can be administered by a healthcare provider in one minute every three weeks or two minutes every six weeks. Berahyaluronidase alfa is a variant of hyaluronidase developed and manufactured by Alteogen Inc.

Dr. Marjorie Green, Senior Vice President and Head of Oncology, Global Clinical Development, Merck Research Laboratories, said, “Keyject is the first and only subcutaneous immune checkpoint inhibitor available in Japan that can be administered by a healthcare provider in as little as one minute. This approval is a significant milestone for patients and healthcare providers in Japan and reflects our commitment to advancing new patient-centered care options like Keyject that offers patients two dosing options and more choices of health care settings where they can receive therapy.”

The approval is based on results from the pivotal Phase 3 MK-3475A-D77 trial, which compared Keyject with Keytruda, both administered every six weeks in combination with chemotherapy, in patients with treatment-naïve metastatic non-small cell lung cancer (NSCLC) without EGFR, ALK or ROS1 genomic tumour aberrations.

The trial demonstrated comparable pharmacokinetic exposure levels between Keyject and Keytruda. In descriptive analyses, overall response rates (ORR) were consistent between the two treatments. 

Study 3475A-D77 was a multicentre, randomised, open-label, active-controlled Phase 3 trial conducted in patients with treatment-naïve metastatic NSCLC without EGFR, ALK or ROS1 genomic tumour aberrations. The primary outcome measures were pembrolizumab exposure during Cycle 1 and at steady state in patients receiving Keyject compared with Keytruda. Additional descriptive efficacy measures included ORR and PFS by blinded independent central review (BICR), as well as OS.

A total of 377 patients were randomised in a 2:1 ratio to receive either Keyject (790 mg/9,600 units) every six weeks with platinum doublet chemotherapy (n=251) or Keytruda (400 mg) every six weeks with platinum doublet chemotherapy (n=126).

Subcutaneous administration delivers medicines under the skin and may provide additional convenience by offering more options for treatment settings, including infusion centres, doctors’ offices and community-based clinics. For patients who do not require a port or have difficult venous access, subcutaneous administration may also simplify treatment administration.

Keytruda is an anti-programmed death receptor-1 (PD-1) therapy that works by increasing the ability of the body’s immune system to help detect and fight tumour cells. It is a humanised monoclonal antibody that blocks the interaction between PD-1 and its ligands, PD-L1 and PD-L2, thereby activating T lymphocytes that may affect both tumour cells and healthy cells.

In September 2025, the US Food and Drug Administration (FDA) approved Keytruda Qlex, which is now approved for adults in the same solid tumour indications as Keytruda. The European Commission approved subcutaneous pembrolizumab, known as Keytruda SC in the European Union, in November 2025, and it is now approved for all Keytruda indications in Europe.