Cabaletta Bio, Inc. announced that the U.S. Food and Drug Administration (FDA) has granted Orphan Drug Designation (ODD) to CABA-201, a 4-1BB-containing fully human CD19-CAR T cell investigational therapy, for the treatment of idiopathic inflammatory myopathies (IIM, or myositis). CABA-201 is in development as a potential treatment for autoimmune diseases driven by B cells. Four RESET?

(REstoring SElf-Tolerance) Phase 1/2 trials are advancing for the evaluation of CABA-201 across multiple autoimmune conditions, including the Phase 1/2 RESET-Myositis? trial. The FDA grants Orphan Drug Designation to drugs or biologics intended to treat or prevent rare diseases or conditions that affect fewer than 200,000 individuals in the United States.

This designation qualifies Cabaletta for certain incentives, which may include partial tax credit for clinical trial expenditures, waived user fees and potential eligibility for seven years of marketing exclusivity. The RESET-Myositis? trial is a Phase 1/2 open-label study of CABA-201 in subjects with active idiopathic inflammatory myopathy (IIM, or myositis), including the subtypes of dermatomyositis (DM), anti-synthetase syndrome (ASyS) and immune-mediated necrotizing myopathy (IMNM).

Subjects will receive a one-time infusion of CABA-201 at a dose of 1 x 106 cells/kg, preceded by a standard preconditioning regimen of fludarabine and cyclophosphamide. Key inclusion criteria include patients between ages 18 to 65 (inclusive), evidence of active disease and disease activity despite prior or current treatment with standard of care treatments. Key exclusion criteria include cancer-associated myositis, significant lung or cardiac impairment, treatment with a B cell depleting agent within the prior approximately six months or treatment with a biologic agent within the prior approximately three months.

As part of Cabaletta?s CARTA (Chimeric Antigen Receptor T cells for Autoimmunity) strategy, this trial is intended to evaluate the potential ability of CABA-201 to transiently, but fully, eliminate B cells, potentially enabling durable remissions via a ?reset? of the immune system. CABA-201 is designed to deeply and transiently deplete CD19-positive B cells following a one-time infusion, which may enable an ?immune system reset?

with the potential for durable remission off therapy in patients with autoimmune diseases. To date, Cabaletta has received clearance from the FDA for Investigational New Drug (IND) applications for CABA-201 in multiple autoimmune conditions including systemic lupus erythematosus (SLE), myositis, systemic sclerosis (SSc) and generalized myasthenia gravis (gMG). Cabaletta is conducting four Phase 1/2 clinical trials with a total of nine cohorts that can advance simultaneously, employing a similar parallel cohort design and starting dose of 1 x 106 cells/kg without a dose escalation requirement.

Myositis refers to a group of autoimmune diseases characterized by inflammation and muscle weakness. In some cases, myositis may also affect other organs and systems in the body, such as the lungs, heart, or skin. Myositis is classified into several subtypes based on the underlying immune mechanisms and clinical characteristics.

Although the pathogenesis of myositis is not well understood, there are several subtypes thought to be driven by B cells, including dermatomyositis (DM), anti-synthetase syndrome (ASyS) and immune-mediated necrotizing myopathy (IMNM). These three subtypes impact approximately 66,000 patients in the US alone, and typically affect middle-aged individuals, particularly women. All three subtypes can lead to severe functional impairment and may be life-threatening.

Current treatment typically involves medications to suppress the immune system and/or chronic intensive therapies such as intravenous immunoglobulin, or IVIg. Despite these therapies, a significant portion of myositis patients have disease that remains refractory to existing medications.