Third Harmonic Bio is launching with the close of a Series B financing campaign. With total capital to date of $155 million, the company plans to fund development of its lead candidate, THB001, through the next phase of human studies for the initial indication of chronic urticaria. 

Atlas Venture founded and seeded Third Harmonic Bio in 2019 and co-led the $50 million Series A with OrbiMed with participation from BVF Partners. Atlas and OrbiMed also participated in the $105 million Series B, which was led by new investor General Atlantic and co-led by existing investor BVF Partners. Additional new investors in the round included Boxer Capital, RA Capital, RTW, Deep Track Capital, Ajax Health/Zeus, and Commodore Capital. 

THB001 is a first-in-class, oral small-molecule inhibitor of KIT, a cell surface receptor that serves as the master regulator of mast cell function and survival. Given KIT’s function, its inhibition has the potential to blunt mast cell-driven inflammation regardless of the activating signal source, providing the potential for broad therapeutic utility. A Phase 1b proof-of-concept study in cold-inducible urticaria could begin in the second half of 2022. 

“Achieving the selectivity required to target KIT with an oral small-molecule therapy for allergy and inflammation has until now been an intractable drug development challenge,” says Natalie Holles, Chief Executive Officer of Third Harmonic Bio. “As a first-in-class, highly selective KIT inhibitor, we believe THB001 has the potential to revolutionize the treatment of a broad range of mast cell-mediated allergic and inflammatory diseases of the skin, airway, and GI tract.” 

“Allergic and inflammatory diseases represent a significant unmet medical need, and although available therapies have been commercially successful, only a fraction of the diagnosed patient population is adequately treated,” says Rob Perez, Operating Partner at General Atlantic. “THB001, with its unique attributes and oral formulation, represents a true pipeline-in-a-product opportunity with the potential to offer an important new therapeutic option to millions of underserved patients.” 

Beyond chronic urticaria, the company plans to pursue development of THB001 in additional diseases of the skin, airway, and gastrointestinal tract in which mast cells play a known role in the pathophysiology of the condition. 

Third Harmonic Bio is led by Natalie Holles, Chief Executive Officer; Stephen Yoo, MD, Chief Medical Officer; and Howard Davis, PhD, Chief Operating Officer. The company’s Board of Directors is comprised of David Bonita, MD, General Partner, OrbiMed; Michael Gladstone, Partner, Atlas Venture; Natalie Holles, Chief Executive Officer; Mark Iwicki (Chairman), Chief Executive Officer, Kala Therapeutics; Shao-Lee Lin, MD, PhD, Chief Executive Officer, Acelyrin, Inc.; Rob Perez, Operating Partner, General Atlantic; Jason Rhodes, Partner, Atlas Venture; and Martin Seidel, Ph.D., Chief Executive Officer, IFM Therapeutics.