J&J Slashes Enrollee Numbers in Phase 3 Single-Dose COVID-19 Vaccine Trial

Johnson & Johnson (J&J) has cut enrollment from 60,000 to 40,000 for its global phase 3 ENSEMBLE 1 trial evaluating COVID-19 vaccine candidate JNJ-78436735 as a single-dose regimen.

The company made the decision based on how widespread the virus has become, with the drugmaker concluding that a smaller trial makes the most sense since more participants will contract the disease.

The parallel ENSEMBLE I and II studies — conducted in partnership with the U.S. Biomedical Advanced Research and Development Authority and the UK’s National Institute for Health Research — initially planned to enroll up to 90,000 participants worldwide in order to assess whether a single or double-dose vaccine regimen was more effective (DID, Nov. 17). Interim analysis from an earlier phase 1/2a study demonstrated a single vaccine dose delivered a strong immune response and was well-tolerated.

While ENSEMBLE 1 will be halting enrollment, ENSEMBLE 2 is still seeking volunteers and will include up to 30,000 participants, a J&J spokesperson told FDAnews. This means the revised total for J&J’s global phase 3 studies now stands at up to 70,000 enrollees.

“We have already recruited more than 38,000 subjects in the [ENSEMBLE I] study,” Moncef Slaoui, head of Operation Warp Speed, said Wednesday at a press briefing, noting enrollment of more volunteers would stop almost immediately. “With J&J, we decided to cap the recruitment to around 40,000 subjects, which will happen by the end of this week,” Slaoui added.

The N.J.-based drugmaker said it expects to have ENSEMBLE study data available by the end of January. “If the vaccine is safe and effective, an Emergency Use Authorization application could be submitted to the FDA in February,” the J&J spokesperson said. “Other health regulatory applications around the world would be made in parallel.”

Preparing for such an approval, the U.S. government forged a manufacturing pact with J&J in August for 100 million vaccine doses through Operation Warp Speed.And, in October, J&J entered into an advance purchase agreement with the European Commission to provide up to 200 million doses, with an option for an additional 200 million doses.

Importantly, J&J has said its vaccine can be stored at normal refrigeration temperatures of -4 degrees Fahrenheit (-20 Celsius) for two years and between 35.6 to 46.4 degrees Fahrenheit (2 to 8 degrees Celsius) for approximately three months, meaning the product can be shipped using existing distribution channels. ― Jason Scott