Blockbuster cancer, Alzheimer’s drugs shift to self-injections

The treatment paradigm for blockbuster medicines such as the world’s top-selling cancer drug and Alzheimer’s therapies is rapidly shifting. Intravenous (IV) infusions that once required hospital visits and hours of supervision are being replaced by subcutaneous (SC) injections that patients can administer themselves in just minutes at home.

While IV delivers drugs directly into the bloodstream for rapid concentration, SC delivers them through the fatty tissue into capillaries, making absorption slower. However, technologies such as hyaluronidase can accelerate absorption, ensuring comparable efficacy and safety. Clinical trials have confirmed that SC formulations are not inferior to IV, with patients reporting little difference in treatment outcomes.

According to industry sources on Tuesday, the U.S. Food and Drug Administration (FDA) will decide by September 23 whether to approve an SC formulation of Merck’s Keytruda, the world’s top-selling cancer drug. Keytruda generated 41 trillion won ($29.7 billion) in sales last year. Merck has partnered with Korean biotech Alteogen to use its hyaluronidase platform for SC development. If approved, the drug could launch in the U.S. market as early as October. While the IV version required 30 minutes to two hours for infusion, the SC form can be completed in two to three minutes, though still administered in hospitals due to its cancer indication. Merck has said it aims to convert 30–40 percent of Keytruda use to SC within 18–24 months.

Other cancer therapies have already made the switch. Bristol Myers Squibb’s Opdivo, Roche’s Tecentriq, and Johnson & Johnson’s Rybrevant are available in SC formulations.

Global drugmakers are also using SC reformulations as a strategy to extend patent protection. With Keytruda’s patents set to expire in 2028, Merck is seeking to maintain its market position by shifting to SC delivery.

A similar shift has taken place in Alzheimer’s treatment.

Eisai and Biogen’s Leqembi, the first anti-amyloid therapy, received FDA approval in August for its SC version, Leqembi Iqlik, allowing patients to self-inject at home once a week in just 15 seconds. This compares to the IV version, which required hospital visits every two weeks for an hour-long infusion.

According to Eisai, adherence to long-term treatment is crucial for patients with early Alzheimer‘s disease. The subcutaneous formulation streamlines maintenance therapy, improving convenience and access for both patients and caregivers.

Even in the complex field of antibody-drug conjugates (ADCs), Japan’s Daiichi Sankyo is working on SC formulations. The company is applying Alteogen’s ALT-B4 hyaluronidase technology to shorten infusion time for its blockbuster Enhertu from 90 minutes to just five minutes.

“SC formulation has opened new possibilities for ADC therapies,” said Um Min-yong, an analyst at Shinhan Investment. “If SC versions prove effective and safe, adoption will become not just an option but a necessity.”