GSK has agreed to pay up to $750 million for an experimental cancer therapy from the privately owned Chinese biotech Chimagen Biosciences.
The pharmaceuticals group will hand over an undisclosed upfront fee to secure full global rights to the programme.
Chimagen could pocket the rest through milestone payments tied to the drug's progress through development and its eventual commercial success.
The asset is a trispecific T cell-engager, a type of immunotherapy that harnesses the body's own T cells to attack tumours.
GSK plans to develop it for multiple myeloma, the third most common blood cancer, which is diagnosed in roughly 180,000 people worldwide each year.
Existing T cell-engagers have proved highly effective against the disease but have often been dogged by nasty side effects.
Chimagen's drug is designed to tackle that problem by locking onto T cells while homing in on two separate tumour markers, an approach the companies hope will deliver stronger, longer-lasting responses with fewer tolerability issues.
The therapy is expected to enter human trials in 2027.
GSK reckons the prize is worth chasing, pointing to a US market for such treatments in multiple myeloma that could top $10 billion by 2032.
Multiple myeloma remains treatable but incurable, and patients frequently stop responding to the medicines available, making fresh options valuable.
The deal deepens an existing relationship between the two firms, following an earlier agreement under which GSK acquired a different Chimagen cancer drug now in early-stage trials.
Hesham Abdullah, GSK's global head of oncology research, said the transaction advanced the group's ambitions in blood cancer and added a new option for patients facing a complex disease.
Chimagen chief executive Zhenhao Zhou said the tie-up paired his firm's engineering know-how with GSK's global reach.
The agreement remains subject to customary closing conditions.
