MSD records one win, one miss with TL1A drug tulisokibart

Amongst MSD's second-quarter results update this morning is the news that its anti-TL1A antibody tulisokibart was effective in a phase 2 trial in skin disorder hidradenitis suppurativa, but failed a study in a rare lung disorder.

The drug – which MSD acquired as part of its $10.8 billion takeover of Prometheus Biosciences in 2023 – is a key pipeline asset for MSD that analysts have predicted could bring in $4 to $5 billion in peak sales, and has already shown efficacy in a phase 3 ulcerative colitis study.

The company said today that tulisokibart met its primary and key secondary endpoints in a phase 2 trial involving patients with hidradenitis suppurativa, a chronic skin disease – also known as acne inversa – that causes painful lumps, boils, and scarring in areas where skin rubs together.

There was disappointment, however, in a second phase 2 study in patients with systemic sclerosis-associated interstitial lung disease (SSc-ILD), which missed its primary endpoint and will be discontinued. SSc-ILD is a chronic autoimmune disease that leads to inflammation and scarring (fibrosis) in the lungs.

SSc-ILD is a fairly small indication for tulisokibart – dwarfed by its lead indications in ulcerative colitis and Crohn's disease and potential follow-up uses like rheumatoid arthritis, psoriatic arthritis, and spondyloarthritis – but will be a blow to patients as there are limited treatment options for the disease.

TL1A has become a hot topic in immunology and inflammation R&D, with tulisokibart slightly ahead of rival candidates like Teva/Sanofi's duvakitug and Roche's afimkibart, which are also in the final stages of clinical testing.

The tulisokibart news came as MSD – known as Merck & Co in the US and Canada – reported a higher-than-expected 5% rise in second-quarter sales to $16.6 billion, helped by the rollout of a new subcutaneous formulation of its cancer immunotherapy Keytruda (pembrolizumab).

The Keytruda QLEX version of the drug, approved by the FDA last September, made $463 million in the quarter, helping total Keytruda franchise sales grow 5% to $8.4 billion ahead of looming patent expiries for the original IV formulation starting in 2028.

A one-time $5.7 billion charge related to the just-completed $6.7 billion takeover of Terns Pharma and its oral BCR-ABL inhibitor for leukaemia, MK-4208 (formerly TERN-701), tipped MSD into a loss for the quarter.

The company has raised its 2026 revenue forecast to $66.3 to $67.3 billion, from a previous range of $65.8 to $67.0 billion, on the back of the second-quarter performance.