An immunotherapy drug for cancers that was in limbo following Bristol-Myers Squibb’s acquisition of Celgene earlier this year has been returned to its original developer.

Beijing-based drugmaker BeiGene said Monday that it had regained global rights to the PD-1 inhibitor tislelizumab from Celgene. Summit, New Jersey-based Celgene and BeiGene had been developing the drug under a partnership before New York-based BMS acquired Celgene in January for $74 billion. BMS, of course, already markets Opdivo (nivolumab), and investors thus expected Celgene to hand tislelizumab back over to BeiGene, though it was only on Monday that it became official.

As part of the agreement, Celgene is paying BeiGene $150 million. BeiGene is also acquired rights to several Celgene drugs in China, including the chemotherapy agent Abraxane (nab-paclitaxel), the blood cancer drug Revlimid (lenalidomide) and Vidaza (azacitidine).

Shares of BeiGene closed down 3 percent on the Nasdaq Monday and were down 5.6 percent on the Hong Kong Stock Exchange.

In a note to investors Monday, Cowen analyst Yaron Werber noted that while BeiGene will retain rights in China, it may partner tislelizumab outside of China. Still, he wrote, the market for checkpoint inhibitors is competitive, and not many large companies need a PD-1 inhibitor.

There are currently three PD-1 inhibitors on the market: BMS’ Opdivo, Merck & Co.’s Keytruda (pembrolizumab) and Sanofi and Regeneron’s Libtayo (cemiplimab-rwlc). In addition, several PD-L1 inhibitors – which target a ligand of the immune checkpoint PD-1 – are approved: Roche’s Tecentriq (atezolizumab), Pfizer and Merck KGaA’s Bavencio (avelumab) and AstraZeneca’s Imfinzi (durvalumab).

Werber added that despite the competitive state of the market, tislelizumab is derisked because it is in Phase III development for multiple cancers.

In an interview at the American Society of Clinical Oncology earlier this month, BeiGene chief adviser Eric Hedrick said that the company was well-prepared for the as-yet-unofficial scenario in which it regained all rights to tislelizumab, adding that it was “fair to say” other companies lacking a PD-1 inhibitor of their own might be interested in one.

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