MeiraGTx Holdings plc (Nasdaq: MGTX), a clinical-stage genetic medicines company headquartered in London and New York, announced that the FDA has granted Breakthrough Therapy Designation for AAV2-hAQP1, an adeno-associated virus serotype 2 vector encoding human aquaporin-1, for the treatment of Grade 2 and Grade 3 late xerostomia caused by radiotherapy for cancers of the upper aerodigestive tract. The designation adds to the Regenerative Medicine Advanced Therapy (RMAT) designation the FDA had previously granted for the same molecule.
The Breakthrough Therapy Designation application was supported by three-year data from a Phase I dose escalation study of AAV2-hAQP1 in patients with radiation-induced xerostomia. That study generated data showing improvements in patient-reported xerostomia outcomes and increases in salivary flow after a single administration, with no serious treatment-related adverse events reported. MeiraGTx plans to present full three-year data from all cohorts of the Phase I study at a program update scheduled for April 16, 2026.
The company's Phase II AQUAx2 study (NCT05926765) is currently in final enrollment stages. MeiraGTx has aligned with the FDA on clinical requirements for this study to support a potential Biologics License Application (BLA), with the primary endpoint being change from baseline in the Xerostomia Questionnaire at 12 months following a one-time treatment. The company anticipates data 12 months after the last patient is treated, with a potential BLA filing in the first half of 2027 and a targeted US launch in early 2028.
Research context
Radiation-induced xerostomia affects patients who have undergone radiotherapy for head and neck cancers, resulting in chronic dry mouth due to salivary gland damage. No approved gene therapies currently exist for this condition. Available treatments are limited to saliva substitutes, sialogogues such as pilocarpine, and supportive care measures, none of which restore salivary gland function at a cellular level. AAV2-hAQP1 is designed to restore fluid secretion by delivering the aquaporin-1 water channel gene directly to remaining salivary gland cells, a mechanistic approach distinct from symptomatic treatments. No other gene therapy candidates for radiation-induced xerostomia appear to be in late-stage clinical development.