8-K: Protara's TARA-002 Shows Strong Phase 2 LM Trial Results

Protara Therapeutics announced positive interim results from its Phase 2 STARBORN-1 trial for TARA-002 in pediatric Lymphatic Malformations, demonstrating high clinical success rates and a favorable safety profile.

Summary

• Interim results from the ongoing Phase 2 STARBORN-1 clinical trial of TARA-002 in pediatric patients with macrocystic and mixed-cystic Lymphatic Malformations (LMs) were announced.
• The analysis included 12 patients who received at least one dose of TARA-002 as of the November 12, 2025 data cutoff.
• Of the 10 patients who completed treatment, 80% (8/10) achieved clinical success.
• 100% (8/8) of patients who completed the eight-week response assessment achieved clinical success.
• Clinical success is defined as a complete response (90% to 100% reduction in total LM volume) or a substantial response (60% to less than 90% reduction in total LM volume).
• The majority of evaluable patients (7/8) achieved clinical success with only one or two doses of TARA-002.
• One patient with a 1,739 ml macrocystic LM achieved a complete response after requiring all four doses.
• 83% (5/6) of macrocystic patients achieved a complete response, with the remaining patient achieving a substantial response.
• The only mixed-cystic patient treated achieved a complete response.
• Two LM patients have reached the 32-week post-treatment assessment and remain disease-free.
• 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.
• One patient was misdiagnosed with a rare form of cancer and did not respond to treatment, while another withdrew after achieving a notable resolution of their LM.

Sentiment

Score: 8

Explanation: The interim Phase 2 results for TARA-002 in LMs are highly positive, showing strong efficacy and a favorable safety profile, addressing a significant unmet medical need. The connection to the well-established OK-432 further de-risks the program. While general biotech risks remain, the clinical data is very encouraging.

Positives

• High clinical success rates: 80% of patients that completed treatment and 100% of evaluable patients achieved clinical success.
• The majority of evaluable patients (7/8) achieved clinical success with only one or two doses, indicating rapid and effective response.
• Strong response across cyst types: 83% of macrocystic patients achieved a complete response, and the only mixed-cystic patient achieved a complete response.
• Favorable safety and tolerability profile with no serious adverse events (SAEs) reported.
• Two patients remain disease-free at the 32-week post-treatment assessment.
• TARA-002 is developed from the same master cell bank as OK-432, which has been the standard of care in Japan for 30 years and has robust clinical data in over 500 U.S. pediatric LM patients.
• TARA-002 has been granted Rare Pediatric Disease Designation by the U.S. FDA for the treatment of LMs.

Negatives

• One patient was misdiagnosed with a rare form of cancer and did not respond to treatment.
• One patient discontinued treatment due to a Grade 2 adverse event of fatigue.
• Two patients withdrew from the trial prior to the eight-week assessment (one due to misdiagnosis, one after notable resolution).

Risks

• Risks that financial guidance may not be as expected.
• Risks and uncertainties associated with development programs, including the initiation and completion of non-clinical studies and clinical trials and the timing of required filings with the FDA and other regulatory agencies.
• General market conditions.
• Changes in the competitive landscape.
• Changes in strategic and commercial plans.
• Ability to obtain sufficient financing to fund strategic plans and commercialization efforts.
• Having to use cash in ways or on timing other than expected.
• The impact of market volatility on cash reserves.
• Failure to attract and retain management and key personnel.
• The impact of general U.S. and foreign, economic, industry, market, regulatory, political or public health conditions.
• Risks and uncertainties associated with business and financial condition in general, including those described more fully under the caption Risk Factors in SEC filings.

Future Outlook

Protara Therapeutics intends to continue its development plans for TARA-002, including future clinical trials and interactions with the FDA. The company anticipates TARA-002 will demonstrate significant clinical benefit and emerge as an important intervention for pediatric LM patients. Protara is also developing TARA-002 for non-muscle invasive bladder cancer (NMIBC) and IV Choline Chloride for patients on parenteral nutrition.

Management Comments

• "We are pleased to report these robust results from the STARBORN-1 trial that demonstrate TARA-002s expected significant clinical benefit in treating patients with macrocystic and mixed cystic LMs." 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." Jesse Shefferman, Chief Executive Officer of Protara Therapeutics.
• "The totality of available clinical data, including data from prior studies with TARA-002s 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." Jesse Shefferman, Chief Executive Officer of Protara Therapeutics.
• "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." Jesse G.A. Jones, M.D., Associate Professor, Department of Neurosurgery and Radiology, University of Alabama at Birmingham, and STARBORN-1 study investigator.

Industry Context

Lymphatic Malformations (LMs) represent a significant pediatric rare disease opportunity with no currently approved therapies. Current treatment options, such as surgical excision or off-label sclerosants, carry high complication rates, recurrence risks, and challenging side effects, especially for pediatric patients. TARA-002 aims to address this high unmet medical need by potentially becoming the first FDA-approved therapy for macrocystic and mixed cystic LMs. The incidence of LMs is 1,400-1,800 cases per year, with an estimated 20,000 patients seeking treatment.

Comparison to Industry Standards

• TARA-002's interim STARBORN-1 data indicate comparable safety and efficacy to its predecessor compound, OK-432.
• OK-432 has been the standard of care for LMs in Japan for 30 years and has shown strong safety and efficacy results in over 500 U.S. pediatric LM patients in a University of Iowa-led study.
• Historically, OK-432 demonstrated 69% clinical success in an immediate treatment group 6 months after enrollment and 84% clinical success in patients with macrocystic lesion types.
• TARA-002's 100% clinical success rate in evaluable patients and 80% in patients completing treatment compares favorably to OK-432's historical data, suggesting a strong potential for TARA-002 to meet or exceed the established efficacy of its predecessor.
• Current treatment options (surgical excision, off-label sclerosants) have high complication/recurrence rates and significant side effects, highlighting TARA-002's potential to offer a safer and more effective FDA-approved alternative.

Stakeholder Impact

• Shareholders: Positive clinical data could lead to increased investor confidence and potential share price appreciation.
• Patients (pediatric LMs): Offers hope for the first FDA-approved, effective, and safe treatment for a debilitating rare disease with high unmet need.
• Medical Community: Provides a promising new therapeutic option for LMs, potentially shifting the standard of care.
• Employees: Positive trial results can boost morale and validate ongoing research and development efforts.

Next Steps

• Continue the ongoing Phase 2 STARBORN-1 clinical trial, including age de-escalation cohorts.
• Further interactions with the U.S. Food and Drug Administration (FDA) regarding TARA-002.
• Potential initiation of Phase 2 trial cohort for NMIBC BCG-Nave TARA-002 Systemic Priming + maintenance (currently in pre-clinical studies).
• Development of IV Choline Chloride for patients on parenteral nutrition.

Key Dates

Recommendation

The interim Phase 2 STARBORN-1 trial results for TARA-002 in pediatric Lymphatic Malformations are exceptionally strong, demonstrating 100% clinical success in evaluable patients and a favorable safety profile with no serious adverse events. This addresses a significant unmet medical need where no FDA-approved therapies currently exist. The strong correlation to OK-432, a compound with 30 years of established use and robust data in Japan, further de-risks the program. Given the high efficacy, safety, and the large market opportunity in a rare disease, TARA-002 has substantial potential for regulatory approval and commercial success, making Protara Therapeutics a compelling investment.

Keywords

Protara Therapeutics, TARA-002, Lymphatic Malformations, LMs, STARBORN-1, Phase 2 clinical trial, pediatric rare disease, biotechnology, cell-based therapy, OK-432, Rare Pediatric Disease designation, clinical success, safety profile, oncology, NMIBC, IV Choline Chloride