Arm covered in hives from a skin allergy.
[Source: gokhanilgaz/Getty Images]

Third Harmonic Bio, a company focusing on developing treatment for severe allergy and inflammatory conditions, came out of stealth mode this week and officially launched with a $155M Series B fundraising round.

The company is based in Cambridge Massachusetts and was founded by Atlas Venture in 2019 who also provided seed funding and co-led a $50M Series A that was not announced to the public. OrbiMed co-led the Series A and also participated in the Series B along with Atlas.

The Series B was led by a new investor, General Atlantic, and co-led by BVF Partners which had previously invested in the company. Boxer Capital, RA Capital, RTW, Deep Track Capital, Ajax Health/Zeus, and Commodore Capital all contributed to the new round.

The company’s lead candidate is a treatment for chronic inducible or spontaneous urticaria, a rash of red welts on the skin that can be caused by a trigger such as cold, heat, exercise or pressure (inducible) or have an unknown cause (spontaneous). Some form of urticaria impacts around one percent of the U.S. population and there is an unmet need for effective treatments in this area, as only around half of these individuals respond to first line antihistamine or second line biologic therapy.

The candidate drug, currently known as THB001, was licensed from Novartis, and acts to block the action of KIT, which is a cell surface receptor protein that regulates mast cell function and survival.

Mast cells are immune cells that play an important role in allergic disease. They initially evolved to protect the body against parasites, but can act in a dysfunctional manner in allergic and autoimmune disease and the histamine, proteases, and proteoglycans, as well as other molecules, they release when triggered can cause urticaria and other allergic or inflammatory symptoms.

THB001 is currently being trialled at Phase I for treatment of chronic urticaria, but is also being investigated for undisclosed respiratory and gastrointestinal indications. It has already demonstrated promising mast cell depletion properties in preclinical trials and an earlier Phase Ia trial in healthy volunteers, according to the company.

“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,” said Natalie Holles, CEO of Third Harmonic Bio, in a press statement.

“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.”

Holles has a strong background in biotech and pharma developed over the last 20 years. She was most recently the CEO of gene therapy company Audentes, now Astellas Gene Therapies, which was acquired by Astellas Pharma in 2019. Audentes lead gene therapy candidate, a treatment for X-linked myotubular myopathy, hit the headlines in 2020 and last year when four boys died in a clinical trial of the gene therapy despite good efficacy results for the therapy.

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