United Therapeutics has paid $140 million to buy Thymmune Therapeutics for preclinical regenerative cell therapies focused on the thymus.
The thymus is the organ in the chest that regulates and develops T cells, key fighters in the body’s battles against infection and disease. As people age, the organ becomes smaller and less active. Thymmune has talked up the potential for its technology to reverse the decline, equipping people to fight off cancer and infection, but its near-term focus is on people with a rare disease who are born without a thymus.
United has paid the upfront fee and committed up to $160 million in milestones to buy the technology. The potential future payments are tied to clinical and regulatory milestones that United could pass as it advances the technology through 2031.
Thymmune’s innovation is a process for converting human-induced pluripotent stem cells into thymic cells. Once in the body, the thymic cells could mature into cell types and restore healthy T-cell function. In animals, Thymmune’s lead candidate, THY-100, triggered the formation of a “neo-thymus.”
THY-100 is in preclinical development for congenital athymia. Patients with the ultra-rare disease lack a thymus, making them vulnerable to fatal infections and immune dysregulation. All 49 congenital athymia patients tracked (PDF) in a natural history population from 1991 to 2017 died by three years of age.
Sumitomo Pharma cited the natural history study when seeking FDA approval for Rethymic, which came to market in 2021. The survival rate was 77% one year after treatment with Rethymic. Among patients alive at Year 1, the survival rate was 94% after a median follow-up of 10.7 years. Rethymic is made of cultured thymus tissue that is surgically implanted.
THY-100 is potentially more scalable. The rarity of congenital athymia, which is estimated to affect about 20 live births a year in the U.S., means scalability may be less important in the ultra-rare disease than in other conditions. But United’s plans for the technology go beyond congenital athymia, with transplant tolerance, serious immune-mediated diseases and enhanced longevity for older adults on its roadmap.
The areas United could pursue if THY-100 achieves clinical proof of concept overlaps with the drug developer’s existing areas of activity. United is developing genetically engineered pig kidneys to offer an alternative to people on donor waiting lists, as well as regenerative medicines for conditions including end-stage renal disease and acute liver failure.