Merck’s $9.2 billion buyout of Cidara Therapeutics marks one of its most strategic late-stage pipeline moves in recent years, bringing in a potentially first-in-class antiviral while also opening an entirely new modality platform for future growth. Announced on November 14, the deal delivers CD388 a long-acting, strain-agnostic influenza prevention candidate now in Phase III and integrates Cidara’s Cloudbreak® drug-Fc conjugate (DFC) platform into Merck’s R&D engine. For a company whose pipeline is dominated by oncology and immunology programs, CD388 introduces a rare but highly valuable infectious-disease asset positioned to become a new seasonal revenue driver through the next decade.
What You Need To Know
- Merck’s $9.2B acquisition of Cidara centers on CD388, a late-stage, long-acting, strain-agnostic antiviral for influenza prevention now in Phase III
- Merck’s pipeline has no existing influenza prevention assets, making CD388 a strategic addition that fills a clear respiratory-disease gap
- Cidara’s Cloudbreak® platform adds long-term oncology optionality, including CD73 and dual CD73/PD-1 preclinical immuno-oncology programs.
- CD388 could become a new seasonal blockbuster, leveraging FDA Breakthrough and Fast Track designations for accelerated development.
CD388 is built as a conjugate that links multiple copies of a potent neuraminidase inhibitor to a proprietary Fc fragment, creating a molecule designed to function as a long-acting small-molecule biologic. The candidate is currently being evaluated in the large Phase 3 ANCHOR study for preventing symptomatic influenza in adults and adolescents at high risk of complications. Earlier results from the Phase 2b NAVIGATE trial exceeded primary and secondary endpoints, demonstrating strong prevention of symptomatic, laboratory-confirmed influenza in healthy adults; the program has already secured FDA Breakthrough Therapy Designation and Fast Track status .
For Merck, the strategic rationale is sharply aligned with gaps visible in its current pipeline. According to the company’s publicly disclosed 4Q2025 pipeline, Merck holds only one antiviral in Phase 3 Lagevrio (molnupiravir) for COVID-19 and no clinical-stage programs specifically targeting influenza prevention. The late-stage pipeline otherwise leans heavily toward oncology, with multiple antibody-drug conjugates (ADCs), Keytruda combinations, and immunotherapy candidates in Phase 2 and Phase 3, along with select immunology and metabolic programs . Adding CD388 immediately diversifies the portfolio, giving Merck a foundational influenza prevention asset with strain-agnostic potential a significant differentiator at a time when flu vaccine effectiveness varies year-to-year and high-risk populations remain underserved.
The acquisition also brings forward three additional preclinical and early-development assets from Cidara, all developed on the Cloudbreak® platform. CBO421, a CD73-targeting oncology agent, is currently in IND-enabling development. Two undisclosed preclinical programs one a CD73/PD-1 dual-target construct, the other a CCR5-targeting program extend the platform into immune-modulation and tumor-microenvironment control. Together, these programs lay the groundwork for potential first-in-class DFC-based immuno-oncology therapies.
Merck’s existing oncology pipeline is anchored by Keytruda, along with a robust slate of ADCs including patritumab deruxtecan, ifinatamab deruxtecan, sacituzumab tirumotecan, and MK-5909. While this portfolio is broad, the company has been actively seeking next-generation biologics and novel modalities to maintain leadership as competitors push forward with bispecific, cell therapies, and targeted immunotherapies. Cloudbreak® offers a potentially modular mechanism capable of simultaneously inhibiting disease targets while leveraging Fc-mediated immune engagement an attractive complement to Merck’s ADC and checkpoint inhibitor strategy.
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Merck leadership made clear that CD388 is envisioned as a major growth driver. CEO Robert Davis highlighted the candidate’s potential to provide season-long protection for individuals at high risk of severe influenza outcomes, emphasizing that the compound fits directly into Merck’s “science-led business development strategy” to augment its pipeline with differentiated programs. Merck Research Laboratories President Dr. Dean Li underscored that the acquisition “expands and complements” the company’s respiratory and infectious-disease footprint beyond COVID-19, addressing a global flu burden that causes up to 650,000 deaths annually .
The deal also positions Merck to compete more effectively in an environment where respiratory infections are attracting renewed investment from industry peers. With RSV programs gaining momentum, pneumococcal vaccines expanding to new age groups, and combination respiratory vaccines in development, a long-acting influenza preventive stands out as a high-value differentiator.
With Phase 3 data expected to evolve through 2026 and the ANCHOR trial including an interim analysis in early 2026, CD388 could potentially reach regulatory review on an accelerated timeline. If efficacy holds across a broader population including immunocompromised patients and older adults it could redefine seasonal flu management and create a franchise-level opportunity for Merck.