Johnson & Johnson Launches Phase 3 Clinical Trial of Two-Dose Regimen for JNJ-78436735 COVID-19 Vaccine

Compiled by Fan Dongdong

Recently, Ad26.COV2.S (also known as JNJ-78436735), the COVID-19 vaccine developed by Janssen, a subsidiary of Johnson & Johnson, has entered the late-stage trial phase. The vaccine is currently undergoing the Phase 3 ENSEMBLE trial involving 60,000 participants, which aims to evaluate whether a single dose can prevent COVID-19 infection. Early data have indicated that JNJ-78436735 can elicit an immune response after a single dose; however, the company now seeks to assess the efficacy of a two-dose vaccination regimen through this trial.

This trial will be conducted under the Phase 3 ENSEMBLE 2 program, with an expected enrollment of 30,000 participants, and will run concurrently with the ongoing ENSEMBLE 3 trial. In a statement, Johnson & Johnson said, “In the context of the global pneumonia pandemic, although a potentially safe and effective single-dose prophylactic COVID-19 vaccine would offer significant benefits, Johnson & Johnson aims to develop a more comprehensive and thorough COVID-19 vaccine program driven by scientific data. Therefore, Johnson & Johnson is investigating multiple dosing regimens and administration schedules to evaluate the long-term efficacy of the vaccine JNJ-78436735.”

This week, the trial for this two-dose vaccine has been launched. It is a randomized, double-blind, placebo-controlled trial aimed at evaluating the safety and efficacy of the two-dose vaccine compared to placebo. Patient recruitment is expected to be completed by March 2021, and the trial will last one year. The participants are primarily adults with or without comorbidities that may increase the risk of COVID-19 infection. Notably, the second dose of this vaccine is administered 57 days after the first dose, which is significantly longer than the current schedule for other two-dose vaccines, where most manufacturers typically complete both doses within 28 days.

Johnson & Johnson also stated that the U.S. Department of Health and Human Services’ Biomedical Advanced Research and Development Authority (BARDA) has already invested $1.4 billion in the company’s COVID-19 research and development efforts, with an additional $454 million to be allocated for the Phase 3 ENSEMBLE trial. Like AstraZeneca and the University of Oxford, Johnson & Johnson is a participant in the U.S. government’s “Operation Warp Speed” initiative to accelerate vaccine development. Through partnerships with major pharmaceutical companies, the U.S. government aims to secure 100 million doses of a viable COVID-19 vaccine by January 2021.

Previously, interim results from the Phase I/IIa study of this vaccine showed that a single dose of JNJ-78436735 induced robust neutralizing antibody responses in nearly all participants. The immune responses elicited by the vaccine were similar across all age groups studied, including older adults. However, the development of Johnson & Johnson’s JNJ-78436735 vaccine has not proceeded without setbacks. In October, Johnson & Johnson was forced to temporarily halt related vaccine trials after a volunteer participant developed an unexplained illness, prompting an evaluation and assessment of the volunteer’s condition. Johnson & Johnson stated that the adverse event observed in this trial was an expected occurrence in clinical research.

Johnson & Johnson’s JNJ-78436735 vaccine is a non-replicating adenovirus 26 vector that expresses the stable prefusion spike (S) protein of SARS-CoV-2. In contrast, Johnson & Johnson’s two main competitors both employ mRNA vaccine technology, which involves directly administering mRNA encoding the viral spike protein into the human body to induce protein synthesis and stimulate the production of corresponding antibodies. Recently, Pfizer and BioNTech announced that their mRNA vaccine demonstrated an efficacy rate of over 90%, while Moderna released trial data yesterday showing its vaccine achieved an efficacy rate of up to 94.5%.

Moreover, the drug does not require the stringent storage and transportation conditions mandated for Pfizer’s vaccine. By comparison, Pfizer’s vaccine can be stored in a standard refrigerator for only five days, while long-term cold-chain storage requires temperatures of -75°C. Like Pfizer, Moderna also plans to apply for Emergency Use Authorization (EUA) in the coming weeks.

Reference Source:

1、J&J, erring on caution, tests new 2-dose regimen for COVID-19 vaccine

2、Moderna's coronavirus vaccine is 94.5% effective, according to company data