Biopharma companies focused on infectious disease extended their stock recoveries through the third quarter (Q3), with the BioWorld Infectious Disease Index closing October up 28.98%. The gain marks a strong turnaround from earlier in the year, when the index had fallen 17.83% by the end of April before rebounding to a 4.34% gain by July’s close.

Merck & Co. Inc. is buying Cidara Therapeutics Inc. for $9.2 billion to acquire a late-stage flu candidate and also to outrace blockbuster Keytruda’s looming patent expiration. CD-388, Cidara’s lead candidate, is in a phase III study of adolescents and adults for preventing influenza A and B in those who are at a high risk of developing complications.

Infectious disease biopharma stocks bounced back in June and July, with the BioWorld Infectious Disease Index (BIDI) closing July up 4.34%. This marked a sharp reversal from earlier in the year, as the BIDI had dropped 17.83% by the end of April and 21.04% by the end of May.

Cidara Therapeutics Inc. will meet with the FDA to discuss strongly favorable phase IIb results from its randomized, double-blind, placebo-controlled phase IIb Navigate trial testing CD-388 for the prevention of seasonal influenza in healthy, unvaccinated adults aged 18-64. Meanwhile, shares of the San Diego-based firm (NASDAQ:CDTX) closed June 23 at $44.95, up $23.93, or 113.8%, as Wall Street learned that the study met its primary endpoint, turning up a statistically significant prevention efficacy for each of three dose groups in people given a single shot at the beginning of the flu season.

The ability of influenza virus to rapidly undergo antigenic shift to evade immunity raises the need for effective influenza antivirals with a broad spectrum. In a recent Nature Microbiology article, Cidara Therapeutics Inc. provided preclinical data for their drug-Fc conjugate compound CD-388, which has the potential to be a robust therapeutic option for the universal prevention of both seasonal and pandemic influenza.

The BioWorld Infectious Disease Index (BIDI) faced challenges throughout the year but narrowed its losses, ending down 6.28% after hitting a low of -25.12% in late April. By October, the index was down 12.07% and had declined 8.86% for the year as of Nov. 22. However, in January, the BIDI rebounded slightly, gaining 1.85%.

The BioWorld Infectious Disease Index has struggled to gain ground in 2024 but has held relatively steady in recent months. After ending July down 7.66%, it closed October down 12.07% and sat at an 8.86% decline for the year as of Nov. 22. 

The influenza virus undergoes rapid and frequent antigen shifts that usually force seasonal vaccine updating. The mismatch between vaccine strains and circulating viruses leads to limited vaccine effectiveness, mainly in immunocompromised and older individuals.

Cidara Therapeutics Inc. announced in its Q2 filing that it received IND clearance for its drug-Fc conjugate (DFC) immunotherapy CBO-421 in July of 2024.

The BioWorld Infectious Disease Index (BIDI) has continued to decline in the first four months of 2024, finishing April with a year-to-date decrease of 25.12%. BIDI trailed both the Nasdaq Biotechnology Index, which saw a 4.76% downturn by April’s end, and the Dow Jones Industrial Average, which closed the month with a 0.34% increase for the year. In 2023, BIDI ended the year with a 43.48% decline, preceded by an 83.57% drop in 2022.