Novavax sees some COVID-19 vaccine trial dropout as Pfizer, Moderna rollouts gear up

As more supplies of Pfizer-BioNTech and Moderna’s authorized COVID-19 vaccines arrive, many states are expanding their reach beyond the elderly and into the 65-plus crowd. That broader rollout has created some problems for clinical trials of other experimental shots.

Novavax’s phase 3 trial of its COVID-19 candidate NVX-CoV2373 has received drop-out requests from some participants 65 or older as New York said it’s now vaccinating people of that age group, The Washington Post reported.

One Long Island physician told the Post that the trial site he managed has received a “significant” number of calls asking to be unblinded from the study and that recruitment is getting harder because “all of a sudden the people over 65 became less interested.”

For the phase 3 Prevent-19 trial Novavax launched late December, the Maryland biotech aims to enroll up to 30,000 volunteers across about 115 sites in the U.S. and Mexico. Of those, at least 25% of people are intended to be 65 years of age or older, a group that's at higher risk of serious COVID-19.

In a statement, Novavax said the WaPo article doesn’t match its actual experience. “Prevent-19 phase 3 clinical trial continues to enroll participants at a robust pace with more than 11,000 individuals enrolled, with fewer than 1% requesting to be unblinded to date,” the company said.

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Within the 65 or older age group, these people now make up about 20% of the enrollees, with a slightly higher rate of dropout requests at 2%.

“Prevent-19 is overpowered, and we expect [to] have far more enrollees than needed to demonstrate efficacy,” the company added.

The company does have a separate U.K. trial, which has already finished enrolling more than 15,000 participants, with a data readout expected in the first quarter, according to a company presentation at the J.P. Morgan Healthcare Conference last week. About 27% of volunteers in that phase 3 trial are 65 or older. The company confirmed that the timing for that data readout remains unchanged.

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Different from the mRNA tech used in the Pfizer-BioNTech and Moderna shots, Novavax’s candidate uses an engineered version of the novel coronavirus’ spike protein delivered on a nanoparticle formulation, and adds the company’s proprietary adjuvant, Matrix M, to enhance the immune response. The protein-adjuvant system represents a well-established vaccine approach compared with mRNA, which just saw its first product for widespread use in Pfizer-BioNTech’s Comirnaty (BNT162b2).

While the mRNA shots must be transported in ultracold conditions, Novavax has said its NVX-CoV2373 is stable at normal refrigeration temperatures of around 2 degrees to 8 degrees Celsius.

Novavax’s phase 3 U.S. trial was already delayed as it worked to iron out manufacturing details with the FDA, which has asked the company to produce the phase 3 clinical supply using commercial-scale processes and facilities.

The company, with help from Operation Warp Speed, has established a global supply chain and expects to have an annual capacity of more than 2 billion doses starting this year. Its bulk drug substance manufacturing partners include Fujifilm, Baxter BioPharma and Korea’s SK Bioscience.