Acelyrin, Inc. Closes $250 Million Series B Financing and Announces Licensing of Izokibep, a Late-Stage IL-17A Inhibitor to Treat Inflammatory Diseases

Series B led by Matrix Capital Management, Surveyor-Citadel Capital, and Westlake Village BioPartners

Currently enrolling izokibep in a pivotal trial in uveitis and a Phase 2b trial in axial spondyloarthritis; activities underway for a Phase 2b trial in hidradenitis suppurativa

LOS ANGELES, CA., NOVEMBER 16, 2021 – ACELYRIN, INC., an innovative biopharma company that identifies, acquires, and accelerates the development and commercialization of life-changing therapies, today announced the completion of a $250 million Series B financing led by Matrix Capital Management (“Matrix”), Surveyor-Citadel Capital, and Westlake Village BioPartners. Additional new investors included Cowen Healthcare Investments, Decheng Capital, Marshall Wace, OrbiMed, RTW Investments, Samsara BioCapital, Tybourne Capital Management, and venBio.

ACELYRIN also announced it has entered into an agreement with Affibody AB to develop and commercialize izokibep, a unique, antibody mimetic, interleukin-17A (IL-17A) inhibitor designed to overcome the limitations of existing monoclonal antibodies. The exquisite potency and small molecular size of izokibep enable high exposures and enhanced tissue penetration in a single subcutaneous injection, thereby providing the potential for izokibep to offer meaningfully differentiated efficacy in several autoimmune diseases.

The proceeds from ACELYRIN’s financing will be used predominantly to fund and accelerate the late-stage clinical program for izokibep. Izokibep is enrolling a pivotal trial for the treatment of uveitis, a vision threatening form of inflammation inside the eye, and a Phase 2b trial for the treatment of axial spondyloarthritis (AS), a chronic form of arthritis that primarily affects the spine and enthesites, specialized tissue that connects ligaments and tendons to bone. In addition, ACELYRIN plans to initiate a Phase 2b trial in 4Q2021 for hidradenitis suppurativa (HS), a devastating, chronic inflammatory disease of the exocrine sweat glands characterized by painful, malodorous nodules and abscesses in the axilla, groin and gluteal areas that can become scarred and disfiguring.

“We are pleased to have such strong support from this syndicate of blue-chip investors who recognize our potential to identify, license, and develop transformative therapies that will help millions of people with serious diseases,” said Shao-Lee Lin, M.D., Ph.D., co-founder and chief executive officer (CEO) of ACELYRIN. “This financing will enable us to rapidly advance izokibep, with its well-understood mechanism of action, in new indications and introduce its potential for differentiated efficacy in existing blockbuster indications. We are now well-resourced to advance our lead program, search for and acquire additional programs and set the course for clinical success.”

“ACELYRIN’s founders have a track record of building multibillion-dollar medicines and are showing what’s possible in identifying molecules with great potential to bring life-changing drug therapies to patients,” said Alan Colowick, M.D., managing director, Matrix. “We believe izokibep is the first of many assets that can transform patients’ lives that the company will develop and we are excited about the future of ACELYRIN.”

Dr. Lin added, “At ACELYRIN, our core value is ‘Courageous Caring’ and we believe with hard work, perseverance, and courage we will be able to bring izokibep to patients who desperately need new treatment options. Because of its potential across many indications, izokibep is a pipeline within a program, the first of many programs we’ll build out in our portfolio. We’re looking forward to acquiring future programs.”

A considerable body of evidence demonstrates that izokibep blocks IL-17A more completely and at markedly lower dose levels than approved monoclonal antibodies. With extraordinary potency and small molecular size, izokibep can reach high drug exposure levels through a single subcutaneous injection that monoclonal antibodies require IV administration to achieve. In addition, the molecule’s small size—about a tenth the size of a monoclonal antibody—also enables its potential to reach targeted tissues that may otherwise be inaccessible to the much larger monoclonal antibodies. 

More than 300 patients have been exposed to izokibep to date, many for up to three years. These data confirm the safety profile of izokibep that supports our strategy to more fully evaluate IL-17A inhibition in pursuit of transformative efficacy across many disease states.

“As the innovators of izokibep, we’re honored to work with ACELYRIN on unlocking this molecule’s potential to address promising new indications and solve unmet needs,” said David Bejker, CEO of Affibody AB. “In addition, we look forward to working with the ACELYRIN team to select additional targets and build new programs, in parallel with the development of izokibep.”

Under the terms of the transaction with Affibody AB, ACELYRIN has obtained worldwide rights to izokibep except development and commercialization by Inmagene Biopharmaceuticals Co., Ltd. in selected Asian countries, including China, Hong Kong, South Korea, and Taiwan, and excluding Japan, and commercialization by Affibody in the Nordic Countries. The agreement with Affibody AB also includes an option for ACELYRIN to license additional molecules developed by Affibody AB. Financial terms of the agreement were not disclosed.


ACELYRIN, INC. is a biopharma company focused on providing patients life-changing new treatment options by identifying, acquiring, and accelerating development and commercialization of promising drug candidates by leveraging its expertise to rapidly advance these medicines to patients. The company was founded in late 2020. For more information, visit

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