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Abcuro announces $66 million Series D financing to advance its first-in-class Medicine in development for Inclusion Body Myositis. * Proceeds to support a potentially registrational clinical study in less severe inclusion body myositis (IBM) patients expected to begin in Q4 2026 and report top line results in 2H 2028 * Ulviprubart showed a trend toward clinically meaningful slowing of disease progression in patients with less severe IBM in the previous Phase 2/3 MUSCLE study * Series D financing led by New Leaf Venture Partners, joined by Abcuro's existing investors and new investor Rock Springs Capital Newton, Massachusetts, August 18, 2026 - Abcuro, Inc., a clinical-stage biotechnology company developing therapies for the treatment of autoimmune diseases through precise modulation of cytotoxic T cells, today announced the closing of a $66 million Series D financing led by current investor New Leaf Venture Partners with participation of existing investors including funds managed by abrdn Inc., Bain Capital Life Sciences, Samsara BioCapital, Redmile Group, Mass General Brigham Ventures, RA Capital Management, Pontifax, Sanofi Ventures, Foresite Capital, NEA, Eurofarma Ventures, Kaitai Capital, Soleus Capital, Nancy Chang, Shang Bay and joining the round is Rock Springs Capital. Proceeds from the Series D financing will support a new potentially registrational clinical study of ulviprubart, a first-in-class monoclonal antibody targeting killer cell lectin like receptor G1 (KLRG1), for the treatment of patients with less severe IBM. Abcuro has been in discussions with the U.S. Food and Drug Administration (FDA) and expects to initiate the new study in the fourth quarter of this year. Assuming positive results from the clinical study, Abcuro plans to file a biologics license application (BLA). "We are pleased to have this opportunity to further evaluate ulviprubart in patients with IBM, a devastating progressive disease," said Alex Martin, Chief Executive Officer of Abcuro. "We have begun preparations to initiate a clinical trial in the fourth quarter of 2026 as we continue our work to develop an effective treatment option in an indication where there is no approved therapy. We remain dedicated to the IBM community and thank our investors who share our conviction in ulviprubart's potential." Results from the recent Phase 2/3 MUSCLE study of ulviprubart in patients with IBM were presented at the 6th Global Conference on Myositis (GCOM) meeting in March 2026. The clinical data, while not statistically significant, showed a trend toward slowing of disease progression relative to placebo as measured by IBMFRS in the overall patient population, including a 50% slowing of disease progression in a pre-defined analysis of less severe IBM patients with IBMFRS >29. Ulviprubart was also shown to have a favorable safety and tolerability profile compared to placebo. "The MUSCLE study provided encouraging data in a pre-defined analysis of patients with less severe disease, underscoring ulviprubart's unique mechanism of targeting highly differentiated cytotoxic T cells expressing KLRG1," said Namita Goyal, MD, Chief of the Neuromuscular Division at the University of California, Irvine School of Medicine. "IBM continues to be a disabling, progressive disease with no approved treatment, affecting tens of thousands of patients around the world. Ulviprubart demonstrated clear and meaningful slowing of disease progression in less severe disease, offering real hope to patients, care partners, and the physicians who treat them." "There is a significant unmet need for an approved treatment for IBM. The expertise and persistence of the Abcuro team to understand this disease and the role ulviprubart may have in targeting these cytotoxic T cells that are associated with muscle destruction was key to our continued investment of the company. We are excited to work closely with the company as it moves forward in this next chapter," said Ron Hunt, Co-Founder and Managing Director of New Leaf Venture Partners. About Ulviprubart Ulviprubart is a first-in-class, potent, monoclonal antibody that targets pathogenic T cells that express killer cell lectin-like receptor G1 (KLRG1) on their cell surface, referred to as KLRG1+ T cells. Ulviprubart is designed to selectively target and deplete well-differentiated cytotoxic KLRG1+ T cells where KLRG1 is highly expressed, while sparing other immune cells, which may offer improvements in safety and tolerability as compared to other T cell depleting approaches. About Inclusion Body Myositis (IBM) IBM is a rare, debilitating and relentlessly progressive chronic autoimmune muscle disease with no approved pharmacologic treatments and a significant unmet need. It is mediated by highly differentiated T cells that are chronically or aberrantly overstimulated and can have detrimental long-term effects including destruction of healthy muscle tissue. People living with IBM progressively lose muscle function, including loss of grip, dexterity and mobility. Based on published epidemiology literature, the ICD-10 code for IBM and an estimate for those misdiagnosed or undiagnosed, Abcuro estimate there are approximately 40,000 patients diagnosed with IBM in the United States and Abcuro estimate the prevalence of IBM to be approximately 35,000 patients across major European countries and Japan. Abcuro estimate that patients with less severe disease represent nearly 50% of the overall IBM patient population. About Abcuro Abcuro is a clinical stage biotechnology company developing potentially first-in-class immunotherapies designed to benefit people living with debilitating and progressive rare autoimmune diseases and for other indications where certain cytotoxic T cells are pathogenic. Abcuro believe that by selectively targeting and depleting highly cytotoxic T cells, which are key drivers of chronic inflammation and damage, Abcuro can advance its mission to deliver potentially life-transforming, disease-modifying therapies to patients facing these devastating conditions. The company's lead program, ulviprubart, is currently being evaluated in inclusion body myositis (IBM). For more information, visit Abcuro on LinkedIn and at abcuro.com.

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