Protara Therapeutics, Inc. recently announced positive interim results from its ongoing Phase 2 open-label STARBORN-1 trial assessing intracystic injection of TARA-002, the Company’s investigational cell-based therapy, in pediatric patients with macrocystic and mixed cystic lymphatic malformations (LMs).

“We are pleased to report these robust results from the STARBORN-1 trial that demonstrate TARA-002’s expected significant clinical benefit in treating patients with macrocystic and mixed cystic LMs,” said Jesse Shefferman, Chief Executive Officer of Protara Therapeutics. “Treatment with TARA-002 resulted in clinically meaningful responses, with a favorable safety profile observed across all evaluable patients. The totality of available clinical data, including data from prior studies with TARA-002’s predecessor compound OK-432, an established treatment for LMs in Japan, underscore our belief in the potential for TARA-002 to emerge as an important intervention for pediatric patients suffering from LMs.”

“There are currently no approved therapies for LMs, with many patients turning to invasive surgical procedures that carry high rates of complication and recurrence, or off-label use of chemotherapies and chemicals, which can have challenging side effects, especially for pediatric patients,” said Jesse G.A. Jones, M.D., Associate Professor, Department of Neurosurgery and Radiology, University of Alabama at Birmingham, and STARBORN-1 study investigator. “I am encouraged by the positive interim safety and efficacy data from TARA-002 and believe this promising candidate has the potential to help the many patients in need of FDA-approved therapeutic approaches for LMs.”

The interim analysis includes a total of 12 patients who enrolled in the trial and received ≥ 1 dose of TARA-002 as of the November 12, 2025 data cutoff. Of those, eight patients were evaluable at an eight-week post-treatment assessment, two withdrew prior to the eight-week assessment and two remain in dosing.  Patients receive up to four injections of TARA-002 spaced approximately six weeks apart. Of the eight patients who were evaluable, the majority (7/8) achieved clinical success with one or two doses. Only one patient, who presented with a 1,739 ml macrocystic LM, required all four doses, and achieved a complete response.

• 80% (8/10) of patients that completed treatment achieved clinical success
• 100% (8/8) of patients who completed the eight-week response assessment achieved clinical success
• 83% (5/6) of macrocystic patients achieved a complete response (90% to 100% reduction in total LM volume) and one patient achieved a substantial response (60% to less than 90% reduction in total LM volume)
• The only mixed cystic patient treated achieved a complete response
• Two LMs patients reached the 32-week post-treatment assessment and remain disease-free
• One patient deemed a complete response was subsequently diagnosed with a ranula (a different type of maxillofacial cyst from LMs)
• Two patients withdrew before the eight-week post-treatment assessment:
  -One patient was misdiagnosed and had a rare form of cancer and did not respond to treatment
  -One patient dropped out after achieving a notable resolution of the patient’s macrocystic LM. The patient received two doses of TARA-002 with 160 ml aspiration at the first dose, which was reduced to a 10 ml aspiration at second dose.

The majority of adverse events (AEs) were mild to moderate, with no serious AEs reported.  The most common AEs were swelling and fatigue. One patient discontinued treatment due to a Grade 2 AE of fatigue.

STARBORN-1 is a Phase 2 single-arm, open-label, prospective clinical trial evaluating the safety and efficacy of intracystic injection of TARA-002 for the treatment of macrocystic and mixed cystic LMs (≥ 50% macrocystic disease) in 29 participants six months to less than 18 years of age. The trial includes age de-escalation safety lead-in cohorts of children ages six years to less than 18 years, two years to less than six years and six months to less than two years. Assessment of efficacy is based on the proportion of participants with macrocystic and mixed cystic LMs who demonstrate clinical success, defined as having either a complete response (90% to 100% reduction from baseline in total LM volume) or substantial response (60% to less than 90% reduction in total LM volume) as measured by axial imaging or via investigator assessment (physical exam, visual inspection and ultrasound). More information about the trial is available at clinicaltrials.gov (identifier: NCT05871970).

TARA-002 is an investigational, genetically distinct strain of streptococcus pyogenes that is inactivated while retaining its immune-stimulating properties. It was developed from the same master cell bank as OK-432, which was originally granted marketing approval by the Japanese Ministry of Health for the treatment of LMs and has been the standard of care in Japan for 30 years. In addition, OK-432 was studied in a large Phase 2 trial in LMs in over 500 patients with significant clinical success. TARA-002 has been granted Rare Pediatric Disease designation by the U.S. Food and Drug Administration for the treatment of LMs.

Lymphatic malformations (LMs) are rare, congenital malformations of lymphatic vessels resulting in the failure of these structures to connect or drain into the venous system. Most LMs are present in the head and neck region and are diagnosed in early childhood during the period of active lymphatic growth, with more than 50% detected at birth and 90% diagnosed before the age of three years. The most common morbidities and serious manifestations of the disease include compression of the upper aerodigestive tract, including airway obstruction requiring intubation and possible tracheostomy dependence; intralesional bleeding; impingement on critical structures, including nerves, vessels and lymphatics; recurrent infection; and cosmetic and other functional disabilities.

Protara is a clinical-stage biotechnology company committed to advancing transformative therapies for people with cancer and rare diseases. Protara’s portfolio includes its lead candidate, TARA-002, an investigational cell-based therapy in development for the treatment of non-muscle invasive bladder cancer (NMIBC) and lymphatic malformations (LMs). The Company is evaluating TARA-002 in an ongoing Phase 2 trial in NMIBC patients with carcinoma in situ who are unresponsive or naïve to treatment with Bacillus Calmette-Guérin, as well as a Phase 2 trial in pediatric patients with LMs. Additionally, Protara is developing IV Choline Chloride, an investigational phospholipid substrate replacement for patients on parenteral nutrition who are otherwise unable to meet their choline needs via oral or enteral routes. For more information, visit www.protaratx.com.