Biogen Inc. (NASDAQ: BIIB) has entered into a definitive agreement to acquire TJ Biopharma's exclusive rights to felzartamab in the Greater China Region for up to $850 million, the companies announced.

Under the terms, TJ Bio will receive a $100 million upfront payment and is eligible for up to $750 million in potential commercial and sales milestone payments, plus mid-single-digit to low-double-digit percentage royalties on potential net sales in the region. The upfront payment is expected to be recorded by Biogen as an Acquired In-Process Research and Development expense in the second quarter of 2026.

The transaction gives Biogen exclusive worldwide rights to felzartamab, a CD38-directed antibody currently being evaluated in global Phase 3 clinical studies across multiple immune-mediated diseases. Biogen previously acquired worldwide rights excluding the Greater China Region through its acquisition of HI-Bio in July 2024.

Felzartamab is currently under regulatory review by China's National Medical Products Administration following a Biologics License Application submitted by TJ Bio in December 2024 for the treatment of multiple myeloma. The companies have been collaborating since April 2025, when TJ Bio joined Biogen-sponsored Phase 3 trials evaluating felzartamab in IgA nephropathy and primary membranous nephropathy in China.

Biogen will now lead manufacturing and commercial efforts for felzartamab in the Greater China Region, while TJ Bio will serve as the manufacturer for the multiple myeloma indication at its Hangzhou GMP facility. The agreement also transfers to Biogen the responsibilities for milestone payment and royalty obligations under the prior MorphoSys licensing agreement.