The race to tame COVID-19 has morphed from a sprint to a long game as companies continue their development to handle a pandemic that is becoming endemic to the planet. That’s the case with Adagio Therapeutics Inc. as it chases clinical studies and an emergency use authorization (EUA) for its monoclonal antibody, ADG-20, to treat and prevent COVID-19.

“We did not predict the emergence of variants in so quick a time,” Tillman Gerngross, Adagio’s CEO and co-founder, told BioWorld. “That was a wakeup call for everyone.”

Privately held Adagio just completed a $336 million series C financing to give muscle to developing ADG-20, which the company said is distinct from other COVID-19 antibody treatments targeting SARS-CoV-2 because it is able to effectively and durably neutralize a range of sarbecoviruses, including SARS-CoV-2 and emerging variants.

Earlier in April, the company initiated its phase I/II/III Stamp study to determine if ADG-20 can reduce hospitalizations and death in high-risk individuals with mild or moderate COVID-19. The global, multicenter, double-blind, placebo-controlled trial will have more than 100 sites and will be conducted in two parts. The first is to assess the safety and tolerability of a single dose of ADG-20 in 30 ambulatory COVID-19 patients.

Tillman Gerngross, CEO and co-founder, Adagio

Afterward, the seamless phase II/III portion includes an assessment by the proportion of patients with COVID-19-related hospitalization or death within 29 days of ADG-20 administration. The study’s initial data are expected by the end of 2021, the company said, with a possible EUA submission by the end of 2021.

Last July, Gerngross speculated that obstructions for widespread COVID-19 vaccine acceptance would include 60% to 70% efficacy that offer limited protection for perhaps three months, plus messy compliance issues and resistance by anti-vaxxers. Some of that has come to pass and some has not. He said he underestimated the efficacy of vaccines based on what he had seen with other coronavirus programs. However, he’s not displeased with Adagio’s approach.

“What we did differently than others is we chose a strategy that envisioned that it’s not about getting to the clinic quickly,” he said. “From the beginning we felt intramuscular injection is important. When you’re treating thousands of people, I.V. not a convenient way to do it. It’s that approach that resonated.”

In February, Adagio began its phase I study of ADG-20 in healthy adults in COVID-19 infection. In addition to the primary endpoints of safety and tolerability, secondary endpoints include pharmacokinetics and immunogenicity, with study exploring serum neutralizing activity ex vivo against SARS-CoV-2.

The Waltham, Mass.-based company is also initiating a third clinical trial in the second quarter of 2021, evaluating ADG-20 for symptomatic COVID-19 prevention.

In July, Adagio, a spinout of Adimab LLC, raised $50 million in a series A to develop its antibodies. Gerngross said he was not looking for government funding, which he said would lengthen and unnecessarily complicate the development cycle.

Adagio raised an $80 million series B for developing ADG-20 in November.

The series C financing was led by RA Capital Management. New investors included Redmile Group, Federated Hermes, Foresite Capital, Arrowmark Partners and PremjiInvest. Existing investors Fidelity Management & Research Co. LLC, Orbimed, Polaris Partners, Mithril, GV, Population Health Partners, Adimab and Omega Funds also participated.

Others developing monoclonal antibodies for COVID-19

Vir Biotechnology Inc., Wuxi Biologics, the U.S. National Institute of Allergy and Infectious Diseases, Biogen Inc., Xencor Inc., Glaxosmithkline plc and Samsung Biologics Co. Ltd. are collaborating on a phase III study of monoclonal antibodies VIR-7831 and VIR-7832 targeting SARS-CoV-2. As of March 26, an EUA had been submitted. A combination of Eli Lilly and Co.’s bamlanivimab and VIR-7831 demonstrated a 70% relative reduction in persistently high SARS-CoV-2 viral load at day seven compared to placebo for low-risk adults with mild to moderate COVID-19, meeting the primary endpoint in the expanded phase II Blaze-4 trial.

Just-Evotec Biologics Inc. and Ology Bioservices Inc. are in a phase I study of ADM-03820, monoclonal antibodies being developed, like ADG-20, as a treatment and/or prophylaxis for COVID-19. The U.S. Department of Defense awarded the companies $28.6 million to produce the antibodies.

In March, Sorrento Therapeutics Inc. and the Icahn School of Medicine at Mount Sinai entered an exclusive license agreement for a collection of antibodies having SARS-CoV-2 neutralizing properties that were developed by Mount Sinai, with the possibility of a development deal for humanized monoclonal antibodies. The collaboration produced Covishield, a combination of two monoclonal antibodies for protecting against disease caused by existing and emerging SARS-CoV-2 variants.

BioWorld is tracking COVID-19 therapeutics and vaccines in development.