Palvella Therapeutics, Ligand Pharma expand partnership to speed up development of Qtorin rapamycin
Palvella Therapeutics Inc, a clinical-stage biopharmaceutical company developing and commercializing novel therapies to treat patients suffering from serious, rare genetic skin diseases for which there are no US FDA-approved therapies, and Ligand Pharmaceuticals Inc, a biopharmaceutical company enabling scientific advancement through supporting the clinical development of high-value medicines, announced the expansion of their strategic partnership to accelerate phase 3 development of Qtorin rapamycin for the treatment of Microcystic Lymphatic Malformations (Microcystic LMs).
“We are pleased to expand our strategic partnership with Ligand Pharmaceuticals, a recognized leader with an established track record in partnering with rare disease companies to accelerate development of high-value therapies,” said Wes Kaupinen, founder and chief executive officer of Palvella. “With an estimated more than 30,000 diagnosed patients in the US suffering from Microcystic Lymphatic Malformations, we see a very significant and attractive commercial opportunity for Qtorin rapamycin as the first potential FDA-approved therapy for this lifelong disease which causes significant patient morbidity from a very young age.”
According to the terms of the amended agreement, Palvella received an upfront payment of $5 million from Ligand. In return, Ligand’s existing tiered royalty on worldwide commercial sales of Qtorin rapamycin increased to 8.0–9.8%. Additionally, Ligand was granted an option to acquire a single-digit royalty on each novel topical product candidate generated from Palvella’s Qtorin platform which can be exercised at a future date.
“Based on the positive phase 2 results announced earlier this year and FDA’s recent granting of Breakthrough Therapy Designation, we are encouraged by the significant commercial potential of Qtorin rapamycin to be the first US FDA approved therapy for Microcystic Lymphatic Malformations in the US,” said Matt Korenberg, president and chief operating officer of Ligand.
Qtorin rapamycin, the lead product candidate from Palvella’s Qtorin platform, is a novel, 3.9% rapamycin anhydrous gel currently under development for the treatment of Microcystic LMs and other serious, functionally debilitating skin diseases driven by the overactivation of the mammalian target of rapamycin (mTOR) pathway. There are currently no FDA-approved treatments for the estimated more than 30,000 diagnosed patients with Microcystic LMs in the US.
Palvella previously announced positive phase 2 results from a multi-center, open-label trial of once-daily Qtorin rapamycin in Microcystic LMs. In the phase 2 study, 100% of participants (n=12) were either “Much Improved” or “Very Much Improved” as rated by the Clinician Global Impression of Change after 12 weeks of once-daily Qtorin rapamycin treatment. The US FDA granted Breakthrough Therapy Designation to Qtorin rapamycin for the treatment of Microcystic Lymphatic Malformations in November 2023. Based on the positive phase 2 results and a productive end-of-phase 2 meeting with US FDA, Palvella plans to conduct a pivotal phase 3 study in approximately 50 adult and pediatric patients. In addition to Breakthrough Therapy Designation, the US FDA previously granted Fast Track Designation and Orphan Drug Designation to Qtorin rapamycin for the treatment of Microcystic LMs.
Qtorin rapamycin is protected by multiple issued composition patents in the US and Japan, and pending patent applications broadly covering anhydrous gel formulations of rapamycin in the US, Europe and Japan.

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