Astria Therapeutics, Inc.

Hereditary angioedema (HAE) is a rare autosomal dominant disorder caused by a deficiency in functional C1 esterase inhibitor, a serpin family protein that blocks the activity of plasma kallikrein. Insufficient inhibition of plasma kallikrein results in the overproduction of bradykinin, a vasoactive inflammatory mediator that produces both pain and unpredictable swelling during HAE attacks, with potentially life-threatening consequences. We describe the generation of STAR-0215, a humanized IgG1 antibody with a long circulating half-life (t_1/2) that potently inhibits plasma kallikrein activity, with a >1000-fold lower affinity for prekallikrein and no measurable inhibitory activity against other serine proteases. The high specificity and inhibitory effect of STAR-0215 is demonstrated through a unique allosteric mechanism involving N-terminal catalytic domain binding, destabilization of the activation domain, and reversion of the active site to the inactive zymogen state. The YTE (M252Y/S254T/T256E) modified fragment crystallizable (Fc) domain of STAR-0215 enhances pH-dependent neonatal Fc receptor binding, resulting in a prolonged t_1/2 in vivo (∼34 days in cynomolgus monkeys) compared with antibodies without this modification. A single subcutaneous dose of STAR-0215 (≥100 mg) was predicted to be active in patients for 3 months or longer, based on simulations using a minimal physiologically based pharmacokinetic model. These data indicate that STAR-0215, a highly potent and specific antibody against plasma kallikrein with extended t_1/2, is a potential agent for long-term preventative HAE therapy administered every 3 months or less frequently. SIGNIFICANCE STATEMENT: STAR-0215 is a YTE-modified immunoglobulin G1 monoclonal antibody with a novel binding mechanism that specifically and potently inhibits the enzymatic activity of plasma kallikrein and prevents the generation of bradykinin. It has been designed to be a long-lasting prophylactic treatment to prevent attacks of HAE and to decrease the burden of disease and the burden of treatment for people with HAE.

Corticosteroids are recommended to all people with Duchenne as standard of care; patient experience data is important to guide corticosteroid decision making and as a comparator for new treatment options.

This study assesses patient and caregiver-reported benefits and side effects from corticosteroids to treat Duchenne muscular dystrophy, their importance, and satisfaction.

Using one-on-one interviews (n = 28) and an online survey (n = 236), parents and adults with Duchenne reported corticosteroid benefits and side effects rated as both experienced and important.

Benefits to breathing, heart function, arm strength, slowing progression of weakness, and getting around were rated as particularly important, regardless of ambulatory status. Important side effects included increased fracture risk, unwanted weight gain, and diabetes/prediabetes. Parents rated behavior issues and adults rated delayed puberty as having high importance. Being ambulatory was independently associated with reporting more net benefit (p = 0.02). For side effects, parent scores were significantly higher than adult score (p = 0.02). Corticosteroid type was not significant. Participants were, overall, satisfied with corticosteroids (means ranging from 6.2 to 7.7 on a scale of 0-10), with no significant differences based on corticosteroid type.

Overall, most participants were satisfied with the use of corticosteroids. While a range of side effects were rated as important and relatively common, individuals using corticosteroids and their caregivers indicate that benefits outweigh the side effects. Qualitative data indicate that high acceptability is influenced by lack of treatment alternatives. Patient experience data on use of corticosteroids in Duchenne may be relevant to drug development, regulatory assessment of new treatments, and to families making decisions about corticosteroid use.

Chronic activation of NF-κB is a key driver of muscle degeneration and suppression of muscle regeneration in Duchenne muscular dystrophy. Edasalonexent (CAT-1004) is an orally-administered novel small molecule that covalently links two bioactive compounds (salicylic acid and docosahexaenoic acid) that inhibit NF-κB. This placebo-controlled, proof-of-concept phase 2 study with open-label extension in boys ≥4-<8 years old with any dystrophin mutation examined the effect of edasalonexent (67 or 100 mg/kg/day) compared to placebo or off-treatment control. Endpoints were safety/tolerability, change from baseline in MRI T₂ relaxation time of lower leg muscles and functional assessment, as well as pharmacodynamics and biomarkers. Treatment was well-tolerated and the majority of adverse events were mild, and most commonly of the gastrointestinal system (primarily diarrhea). There were no serious adverse events in the edasalonexent groups. Edasalonexent 100 mg/kg was associated with slowing of disease progression and preservation of muscle function compared to an off-treatment control period, with decrease in levels of NF-κB-regulated genes and improvements in biomarkers of muscle health and inflammation. These results support investigating edasalonexent in future trials and have informed the design of the edasalonexent phase 3 clinical trial in boys with Duchenne.