Moderna Halts Development of Congenital CMV Vaccine After Phase 3 Trial Disappointment

Moderna, the biotechnology giant known for its mRNA vaccine technology, has announced the discontinuation of its congenital cytomegalovirus (CMV) vaccine program following disappointing results from a large-scale phase 3 trial. The decision marks a significant setback in the ongoing efforts to develop a vaccine against this common viral infection that can cause serious complications in newborns.

Phase 3 Trial Results and Program Discontinuation

The phase 3 trial, which enrolled 7,454 women aged 16 to 40 from 13 countries, revealed that Moderna's mRNA-1647 vaccine candidate fell short of its protective efficacy targets. While the vaccine was well-tolerated, its ability to prevent CMV infection ranged from a mere 6% to 23%, depending on how cases were defined. This efficacy rate was substantially below the company's expectations, leading to the decision to halt further development of the vaccine for congenital CMV prevention.

Stephen Hoge, M.D., Moderna's President, expressed the company's disappointment in a statement: "We are clearly disappointed by the failure to prevent primary infection because it means there is still no vaccine for the prevention of congenital CMV despite the many decades of work by the field."

Implications and Future Directions

Despite this setback, Moderna is not abandoning CMV research entirely. The company will continue to explore the vaccine's potential in preventing CMV reactivation in bone marrow transplant patients through an ongoing phase 2 trial. This study, set to enroll approximately 224 patients, is expected to conclude in August 2026.

Moderna has stated that the discontinuation of the congenital CMV program will not impact its financial guidance for 2025 or its plans to achieve breakeven status in 2028. However, this development, coupled with recent government scrutiny of mRNA vaccines, puts increased pressure on Moderna's oncology pipeline to deliver results.

Shift in Focus to Oncology

In light of these challenges, Moderna appears to be pivoting its focus more heavily towards oncology. Kyle Holen, M.D., Moderna's oncology head, recently indicated that the majority of the company's upcoming investigational new drug applications will be in cancer indications rather than infectious diseases.

At the European Society of Medical Oncology (ESMO) meeting, Moderna presented promising phase 1/2 data for its cancer vaccine mRNA-4359 in combination with Merck & Co.'s Keytruda. The study, involving 29 patients, showed an objective response rate of 24% in evaluable patients. Based on these results, Moderna plans to expand its investigation of mRNA-4359 into lung cancer, signaling a strategic shift in the company's research and development priorities.