Protara Therapeutics, Inc. announced the results of a retrospective analysis of OK-432, the originator compound for TARA-002, the company's investigational therapy in development for the treatment of lymphatic malformations (LMs). LMs are serious, rare, congenital malformations of lymphatic vessels. The results from the analysis, which were presented during a poster presentation at the International Society for the Study of Vascular Anomalies (ISSVA) World Congress 2022, showed that OK-432 was clinically successful and generally well-tolerated in the treatment of both macrocystic and mixed-cystic LMs. The retrospective analysis included 246 patients from a Phase 2 randomized study, and 275 patients from an open-label study.

The majority of participants in both studies were six months to 18 years of age. In the first study, patients were randomized 2:1 to receive treatment immediately (immediate treatment group [ITG]) or delayed by six months (delayed treatment group [DTG]). In the open-label study, patients received four doses of OK-432 approximately six weeks apart.

The primary efficacy endpoint was clinical success (defined as complete [90%-100%] or substantial [60%-89%] reduction in LM volume measured radiographically) in the ITG versus spontaneous resolution of the LM in the DTG. Efficacy was assessed two weeks post-treatment in the randomized study, and one to six months post-treatment in the open-label study. Key findings are summarized: Approximately 69% of patients in the randomized study ITG achieved clinical success after six months, while only 7.5% of patients in the DTG showed spontaneous resolution of LMs in the same time period (p<0.0001); 73.1% of patients in the open-label study achieved clinical success; In the randomized and open-label studies, 10 of 219 (4.6%) and 5 of 275 (1.8%) subjects, respectively, were reported to have treatment emergent serious adverse events that were assessed by the investigator as related to study drug.

The most severe adverse events (SAE) were airway obstruction and facial paralysis due to swelling post-injection that required tracheostomy and hospitalization. Both of these events were reported as resolved. One SAE related to OK-432 led to discontinuation (proptosis of the eye); Local/systemic reactions peaked in the first few days and resolved within two weeks; Patients were followed for up to three years post treatment with no significant safety concerns.