Less than two years after Novartis plunked down $300 million to partner on a clinical-stage cancer immunotherapy from BeiGene, the alliance is ending before the pharmaceutical giant is on the hook for a lot more money.

BeiGene disclosed in a Tuesday regulatory filing that the two companies agreed to mutually terminate the agreement on the drug, ociperlimab. The deal ends before Novartis faced the choice of exercising options on the drug to advance its development in a range of solid tumors. According to the deal terms, Novartis would pay $600 million for exercising its option to start and fund additional global clinical trials with the drug in mid-2023; $700 million if that option was exercised later in the year. Rather than pay those option fees and bankroll those those pricey trials, Novartis is walking away from the BeiGene drug and a target once regarded as the next hot new thing in cancer immunotherapy.

Ociperlimab is a checkpoint inhibitor, a type of drug that blocks proteins that tumors use to evade detection by the immune system. This BeiGene antibody is specifically designed to block TIGIT, a so-called checkpoint protein on immune cells. Blocking TIGIT was hoped to emulate the success achieved by drugs such as Merck’s blockbuster seller Keytruda, which addresses the checkpoint protein PD-1. But the promise of TIGIT has diminished as drugs addressing this target have produced disappointing clinical trial results.

Last year, Roche’s TIGIT blocker tiragolumab failed two closely watched studies in lung cancer. That drug is still in clinical development as part of combination treatments. In March, Merck reported that MK-7684A, a coformulation of anti-TIGIT drug vibostolimab and Keytruda, did not achieve statistical significance on the main goal of showing improvement in progression-free survival.

Meanwhile, the TIGIT alliance between Arcus Biosciences and Gilead Sciences is continuing. Last month, during the annual meeting of the American Society of Clinical Oncology, the partners reported updated Phase 2 results for the TIGIT-blocking antibody domvanalimab paired with an anti-PD-1 drug, zimberelimab. Compared to zimberelimab alone, the combination treatment led to clinically meaningful improvement in overall survival and progression-free survival. Arcus’s TIGIT-blocking drug is being evaluated in four Phase 3 studies in lung and gastrointestinal cancers.

With the Novartis/BeiGene alliance on ociperlimab ending, the Swiss pharma giant is giving back all rights to the drug. BeiGene said in the regulatory filing that it will continue enrollment of a Phase 3 test of the drug in combination with the company’s PD-1-blocking antibody, tislelizumab. This clinical trial is testing the drug in patients with advanced non-small cell lung cancer. But citing the “changing treatment paradigm,” BeiGene said it will discontinue a separate Phase 3 study testing the pairing of ociperlimab and tislelizumab compared to AstraZeneca drug Imfinzi and chemoradiotherapy in stage 3 non-small cell cancer that cannot be treated with surgery.

Image by Flickr user Ed Uthman via a Creative Commons license