Sling Therapeutics is advancing the first late-stage oral drug for thyroid eye disease that, if approved, could compete against Amgen and Viridian Therapeutics.
Sling Therapeutics has raised $123 million in series C money, which the biotech will use to advance an investigational treatment for thyroid eye disease, potentially bringing the first oral drug for the indication to the market.
The proceeds will power Sling’s linsitinib, currently the only late-stage oral small-molecule blocker of the insulin-like growth factor 1 receptor (IGF-1R), a validated target for thyroid eye disease (TED), the biotech said on Wednesday. At the same time, Sling announced the launch of the Phase 3 ORBIT trial for linsitinib, according to a separate release.
ORBIT will test a 150-mg twice-daily dose of linsitinib against placebo, primarily assessing the drug’s ability to reduce the abnormal bulging of the test eye without worsening the other eye—an endpoint defined as proptosis response. The trial has an enrollment goal of 130 patients, with initial data expected in mid-2028, according to a clinical trials database.
In the Phase 2b/3 LIDS trial, linsitinib achieved a 52% proptosis response rate at 24 weeks. The asset’s safety profile was consistent with prior studies, with no drug-related hearing problems or menstrual cycle disruptions observed in patients receiving the 150-mg twice daily dose. Common treatment-emergent adverse events included diarrhea, headaches, nausea and fatigue.
LIDS demonstrated elevations in certain liver enzymes, though these were all “quickly resolved,” and didn’t result in organ dysfunction or liver injuries, Sling said.
The FDA has granted linsitinib fast track designation, which allows for more frequent interactions between the company and the regulator.
Sling’s series C was led by global venture capital firm Forbion, with participation from TPG Life Sciences Innovations and Sectoral Asset Management.
If linsitinib were to gain approval, Sling would potentially go up against Amgen and its intravenous therapy Tepezza, which won approval for TED in 2020. In the second quarter, Tepezza surged 14% year-on-year to $576 million in revenue. Amgen is also developing a subcutaneous version of the drug, which achieved a 76.7% proptosis response rate at 24 weeks in patients with moderate to severe TED, according to a Phase 3 readout in April.
Another TED competitor is Viridian Therapeutics, which itself is a relative newcomer that won the FDA’s go-ahead in June. The company’s asset, called Lumvoa, is also administered intravenously but needs fewer doses than Tepezza.
