Merck shuffles the Kelun deck again

Merck & Co’s work in antibody-drug conjugates is tied to two sizeable licensing deals, one with Kelun Biotech and the other with Daiichi Sankyo, so choosing the right targets and avoiding overlap might require a delicate touch. Perhaps this explains why the Kelun deal has been subject to several revisions since its first iteration two years ago.

The latest shift, Kelun revealed in its interim financials statement yesterday, has seen Merck hand back rights to SKB315/MK-1200, an ADC targeting Claudin18.2 that Merck had taken into a phase 1/2 solid tumour study. However, the US group has picked up a new Kelun project, paying $37.5m for rights to SKB571, which is described as a bispecific ADC against undisclosed targets.

This means that the Merck/Kelun tie-up now comprises five separate transactions, and includes seven different ADCs. The most advanced of these is the anti-TROP2 sacituzumab tirumotecan, the first asset Merck picked up from Kelun in May 2022. The only other known target is Nectin-4, in SKB410/MK-3120, and beyond that there are four undisclosed preclinical projects, plus the new SKB571.

It’s notable how little this periodic opting in and out has cost Merck in up-front fees. For instance, the company paid just $47m for rights to saci-T, though clearly it will have invested far more in its subsequent clinical development.

That work now includes clinical trials seeking to enrol some 10,000 patients across studies sponsored by Merck and Kelun. Yesterday Kelun said China’s NMPA had accepted a saci-T filing for EGFR-mutated NSCLC in the post-EGFR inhibitor and platinum chemo setting, based on the OptiTROP-Lung03 study; Kelun’s first filing, for third-line triple-negative breast cancer on the back of OptiTROP-Breast01, was accepted in December.

Claudin crowd

Just two months after the saci-T deal Merck expanded the Kelun tie-up to pick up SKB315, which it has now handed back to Kelun. No results from Merck’s study of this ADC have been reported, but it’s possible that the decision was prompted by Claudin18.2 becoming extremely crowded; Kelun says it will continue development, and has “confidence in the market prospects of SKB315 in China”.

This isn’t the first time Merck has taken a step back from Kelun: last October it handed back two undisclosed preclinical projects, keeping only five from a December 2022 deal expansion. It’s likely, given the timing of this move, that this was triggered by target overlaps with the Daiichi Sankyo deal, which Merck also signed last October.

At the same time Merck revealed Nectin-4 to be the target of SKB410/MK-3120, and this molecule continues in phase 1. Kelun says it plans IND submissions for other preclinical ADCs under the Merck deal; any hints as to the targets of these assets, and of SKB571, are keenly awaited.

The evolution of Merck's deal with Kelun

Source: company disclosures & OncologyPipeline.