icosavaxVirus-like particle (VLP) technology specialist Icosavax has closed $100 million in Series B financing, which it will use for clinical studies and continued development of a SARS-CoV-2 vaccine candidate.

One focus of the clinical research will be clinical trials for its bivalent respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) vaccine.

RSV is a common respiratory virus that generally causes mild illness but can cause serious complications in infants and the elderly. In a similar vein, hMPV generally causes symptoms consistent with other upper respiratory tract illnesses, but severe infections can require hospitalization. Both viruses are common causes of viral pneumonia. No vaccines are available for either virus.

“VLP vaccines have the potential to be extremely effective,” said Adam Simpson, CEO of Icosavax. “For example, naturally occurring VLPs have delivered effective licensed vaccines, including against human papillomavirus (HPV) and Hepatitis B. But reworking naturally occurring VLPs has been difficult to utilize for the display of complex heterologous antigens, such as RSV or hMPV.”

Icosavax has decided not to rely on molecules that naturally form nanoparticles, “which can be inflexible and limited by their natural configuration,” Simpson said. Instead, the company has opted to “start from scratch and use the power of computational protein design to optimize and create VLP configurations with increased flexibility and ability to display complex antigens.”

Simpson said the computationally designed VLP technology “solves the problem of constructing and manufacturing VLPs displaying complex antigens.” The company’s strategy is to generate two computationally designed proteins that separate the folding of individual protein subunits from the assembly of the final macromolecular structure. “The individual proteins are expressed and purified using traditional recombinant technologies and then self-assemble into VLPs when mixed together,” Simpson said.

Icosavax will use a portion of the funding to continue development work on its SARS-CoV-2 vaccine candidate and to continue expanding its pipeline of vaccine candidates. The company hopes to commence clinical trials involving its SARS-CoV-2 candidate, IVX-411, this year.

The company plans to advance its RSV vaccine candidate, IVX-121, into clinical studies later this year. “Data from the first-in-human study of IVX-121 in young and older adults will inform and enable the transition to a bivalent RSV/hMPV clinical program. IVX-121, incorporates a stabilized prefusion F antigen licensed from NIAID/NIH (DS-Cav1; Science 2019),” Simpson said.

RA Capital Management led the recent funding round, joined by Janus Henderson Investors, Perceptive Advisors, Viking Global Investors, Cormorant Asset Management, Omega Funds and Surveyor Capital. RA Capital Management founder and managing partner, Peter Kolchinsky, will join Icosavax’s board.

Earlier, the Bill & Melinda Gates Foundation awarded a $10 million grant to support the development of the Icosavax COVID-19 vaccine candidate.

Icosavax has an exclusive license for several vaccines from the University of Washington.

The company sees computationally-designed VLP technology as a platform technology with “the potential to generate vaccines against viruses that have been historically intractable to other technologies,” as Simpson put it. “We also see VLPs as an optimal technology for combination vaccines and plan to explore combination vaccines with our future development candidates – starting with a combo RSV+hMPV vaccine candidate,”  he said. “For Icosavax, right now, we are focused on vaccine candidates to protect the elderly from life-threatening respiratory diseases, but the technology itself has broad applicability to other targets we may consider in the future.”