A Phase 1, Double-blind, Randomized Trial to Evaluate Safety and Immunogenicity of Fluzone® High-Dose Influenza Vaccine When Concomitantly Administered With CD388, a Novel Long-Acting Antiviral Conjugate for the Prevention of Influenza

The goal of this clinical study is to investigate how safe and effective it is to receive both the Fluzone® High-Dose (HD) influenza vaccine and CD388, a long-acting antiviral medicine, at the same time. Some participants will receive the vaccine and CD388, while others will receive the vaccine and a placebo. The study aims to determine whether taking CD388 together with the flu vaccine affects the body's ability to build protection-called an immune response-against the flu, as compared to getting the vaccine with a placebo. The hypothesis is that giving both at the same time does not weaken the immune response to the vaccine. The study will measure the amount of antibodies (proteins produced by the immune system to fight flu viruses) generated by participants in both groups to check that CD388 does not interfere with how well the vaccine works. Participants will also be closely watched for any side effects or reactions to check that CD388 is safe to take alongside the vaccine. Expanded access to the study treatments (flu vaccine and CD388) will not be provided to participants after the study ends.

Start Date08 Nov 2025

Sponsor / Collaborator

Cidara Therapeutics, Inc.

NCT07225959

/ Active, not recruitingPhase 2

A Phase 2, Open-Label, Long-Term Study to Evaluate the Safety, Pharmacokinetics, and Occurrence of Anti-Drug Antibodies in Healthy Participants Following Annual Doses of CD388, a Novel Long-Acting Antiviral Conjugate

The goal of this clinical study is to learn if giving repeated annual doses of the experimental drug CD388 is safe and how the body reacts to it in healthy adults who have already received one dose without serious side effects. The study aims to determine if the body makes antibodies against CD388 after repeated doses, which might affect how the drug works or how safe it is, and to better understand the safety and tolerability of repeated doses. Participants will receive two doses of CD388 over two years and be monitored for 18 months. Researchers will check for immune responses against the drug, watch for any side effects, and measure how the drug behaves in the body over time. This study is based on the idea that people who tolerated CD388 well before will likely continue to tolerate it safely with repeated annual dosing, and that the risk of immune reactions will remain low. Expanded access to the study drug will not be provided to participants after the study ends.

Start Date29 Oct 2025

Sponsor / Collaborator

Cidara Therapeutics, Inc.

NCT07159763

/ Active, not recruitingPhase 3

A Phase 3 Randomized, Double-Blind, Placebo-Controlled, Multicenter Study to Evaluate the Safety and Efficacy of CD388, a Novel Long-Acting Antiviral Conjugate, for the Prevention of Influenza in Adults and Adolescents at Higher Risk of Developing Influenza Complications

The purpose of this study is to evaluate how well CD388 works in preventing symptomatic laboratory-confirmed influenza infections, as compared to placebo, when given as a single dose via 3 subcutaneous (SQ) injections to adult and adolescent participants who are at higher risk of developing influenza complications, and to evaluate the safety and tolerability of CD388, as compared to placebo.

Start Date25 Sep 2025

Sponsor / Collaborator

Cidara Therapeutics, Inc.

100 Clinical Results associated with CD-388

100 Translational Medicine associated with CD-388

100 Patents (Medical) associated with CD-388

Literatures (Medical) associated with CD-388

24 Dec 2025·CLINICAL INFECTIOUS DISEASES

Prophylactic Efficacy of CD388, a Novel Drug–Fc Conjugate, in a Human Influenza A/H3N2 Virus Challenge Model: A Randomized, Controlled Phase 2a Study

Article

Author: Wang, Sy-Shi ; Villacian, Jorge ; Tourneroche, Alice ; Silva, Isabel Gonçalves ; Anandakumar, Arun ; Equils, Ozlem ; Baguet, Tristan ; Mann, Alex ; van Duijnhoven, Wilbert ; Vingerhoets, Johan ; Rojas, Roxana E ; Flanagan, Shawn ; Anger, Antoinette

Abstract:

Background:

Influenza is a significant public health concern, especially in immunocompromised patients. CD388 is a novel multivalent zanamivir conjugate that is stably linked to a proprietary human immunoglobulin G1 Fc with a long half-life for prevention of influenza. Here we report a proof-of-concept study on the prophylactic activity of subcutaneously administered CD388 against influenza challenge.

Methods:

In a randomized, double-blind, placebo-controlled, phase 2a human challenge study, a single dose of CD388 (50 or 150 mg) was subcutaneously administered in healthy participants 5 days before intranasal challenge with influenza A (H3N2). Safety, pharmacokinetics, infection rate (by reverse transcription–quantitative polymerase chain reaction methods [RT-qPCR]), intranasal viral load (VL), and symptoms were compared between the CD388 and placebo treatment groups.

Results:

The area under the VL–time curve (VL-AUC), primary endpoint, was lower in the CD388 150 mg group (n = 28) compared with the placebo group (n = 28; mean 10.70 log10 [copies/mL] × days vs mean 16.09 log10 [copies/mL] × days; P = .0390). Peak VL and the rate of RT-qPCR–confirmed influenza infection were lower in the CD388 group versus the placebo group (P = .0185 and P = .0248, respectively). Clinical symptom scores were numerically lower among participants treated with CD388 compared with participants treated with placebo. There were a limited number of treatment-emergent adverse events. Anti-drug antibody development was rare and not clinically relevant.

Conclusions:

CD388 was well-tolerated and demonstrated prophylactic activity against RT-qPCR–confirmed influenza infection in a human challenge study. The efficacy of CD388 in preventing influenza will be confirmed in larger studies.Clinical Trials Registration. ClinicalTrials.gov identifier: NCT05523089.

01 Jul 2025·DRUG METABOLISM AND DISPOSITION

Absorption, distribution, metabolism, and excretion of an antiviral drug-Fc conjugate CD388 following subcutaneous administration of 14C-CD388 in the rat

Article

Author: Cuyckens, Filip ; Ong, Voon ; Laenen, Aline ; Flanagan, Shawn ; Mannens, Geert ; Hough, Grayson ; Snoeys, Jan ; Harris, Stephen

CD388 is a novel drug-Fc conjugate designed to function as a long-acting antiviral drug by inhibiting proliferation of the influenza virus. This action results from a dimeric form of zanamivir, a neuraminidase inhibitor, conjugated to an Fc fragment of recombinant human IgG1 through a noncleavable polyethylene glycol-based linker. In this study, we aimed to demonstrate that, although similar to monoclonal antibody-based molecules, CD388 is distinct in that it maintains stability in vivo for an extended period with minimal biotransformation and achieves prolonged exposure in the lungs, the intended site of therapeutic action. For this purpose, rats received a single subcutaneous administration of 146 mg/kg (655 μCi/kg) radiolabeled CD388 which resulted in a maximal plasma concentration at 24 hours and a terminal half-life of 190 hours. Drug-related radioactivity recovery in urine and feces over a 28-day period was 61% and 15% of the dose, respectively, with a total recovery of 96% ± 2% (cage wash, dose site, and carcass included). ¹⁴C-CD388-related radioactivity was distributed to most tissues and declined slowly beyond 120 hours, remaining widespread throughout the body during the entire sampling time (840 hours). During the period of absorption, the highest radioactivity was observed in the kidney, lung, cardiac blood, lymph duct, and lymph nodes. Based on liquid chromatography-accurate mass spectrometry data, CD388 was the major circulating component in plasma. Radioactivity observed in urine and feces were primarily metabolites containing unmodified dimeric zanamivir plus linker (abbreviated as di-ZAN). No free zanamivir was identified in the analyzed matrices. SIGNIFICANCE STATEMENT: CD388 is a drug-Fc conjugate in development for prevention of influenza. This study showed wide tissue distribution, prolonged clearance of CD388, and evidence that no zanamivir was cleaved from the drug-Fc conjugate. Catabolism of the Fc domain resulted in formation of metabolites containing the unmodified dimeric zanamivir plus linker. These data support the mode of action of CD388 and demonstrate that the conjugation of zanamivir to the Fc domain is stable, thereby enabling CD388 to maintain its potent antiviral activity.

News (Medical) associated with CD-388

17 Nov 2025

·endpoints.news

Five takeaways after Merck's $9.2B Cidara deal: More M&A, 'diversified' growth, shifting production to the US

It appears $19 billion in deals this year is just the beginning of Merck’s plan to build its next chapter. Merck has the world’s top-selling medicine, but it will need a suite of treatments to fill the gap left by Keytruda once the cancer immunotherapy begins to lose patent protection in the coming years. Last week’s $9.2 billion deal for flu antiviral developer Cidara Therapeutics and the $10 billion acquisition of commercial respiratory drugmaker Verona Pharma could help pad sales gaps for Keytruda over the next decade. But Merck is not done hunting. “We look forward to a future with a far more diversified set of growth drivers,” Merck CEO Rob Davis said on a Monday call with analysts to discuss the Cidara acquisition, which is expected to close next quarter. He cited the company’s ability — and perhaps its need — to conduct more deals of up to $15 billion. Here are five more takeaways from the call and Merck’s plans for Cidara’s CD388, a long-acting antibody-drug conjugate in Phase 3 testing for influenza prevention. It’s not a vaccine: Merck executives noted that CD388 would complement its existing work in vaccines and antivirals, such as HIV, but that the molecule isn’t a vaccine. “I just want to continue to emphasize this is not a vaccination. This is an antiviral,” Merck Research Laboratories president Dean Li said. CD388 could be strain-agnostic, have low resistance and help immunocompromised individuals who have a higher risk of flu complications, Merck said in its presentation . “Unlike flu vaccines, efficacy of CD388 should not vary season to season, nor be dependent on immune response. CD388 is designed to provide a full season of coverage from influenza strains A and B, and given its mechanism, it has the potential to be complementary to flu vaccines,” Li said. ‘We want to do more’: Davis said Merck is looking for additional medicines across oncology, immunology, cardiovascular, cardiometabolic and cardiorespiratory diseases. “The $1 billion to $15 billion range is still our primary focus, but as we pointed out, we are willing to go larger than that if we see an asset that brings the scientific benefits I’ve talked about and is aligned to the portfolio,” Davis said. But he’s not looking at a merger with another big pharma: “We continue to believe there is no need for a cost-synergy-driven type of transaction.” On deal value: Given that CD388 is still in Phase 3, Merck executives were asked why they were paying fully in cash upfront, and not sticking some of the potential payout in a contingent value right (CVR), which has been popular this year for assets that are still in trials. “We are very comfortable with the valuation that we have given for this acquisition,” said Merck chief financial officer Caroline Litchfield. “We see it having a high probability of success of making it across the finishing line, and therefore feel we’ve paid a full and fair value for an asset that has the potential to be over $5 billion as we move forward.” Peak sales target, and pricing plans: Merck thinks CD388 could reach annual revenue of $5 billion or more, though analysts are less bullish, projecting a peak of $3.1 billion, according to a note from Cantor Fitzgerald. The medicine is expected to reach the market by the end of this decade. Asked about pricing, Litchfield said Cidara did market research that showed a “price point up to $600 was very effective” for the once-yearly flu prevention tool. “We will look at that research to determine what’s the right price point for ourselves,” Litchfield said. She said the ex-US market would “expect to see fairly comparable prices to the United States.” The Merck CFO said potential US sales of CD388 made up “the most significant part of our valuation” of Cidara. Plans for American manufacturing: With domestic drug manufacturing at the forefront of the Trump administration’s healthcare policies, one analyst called out that Cidara’s commercial strategy for CD388 “leaned heavily on WuXi-manufactured product from China with new CDMOs potentially serving as a back-up.” That will change under Merck. Davis said CD388 will be manufactured in the US, and that Merck will “have to work through the transition with WuXi over time.”

ImmunotherapyAcquisitionPhase 3Vaccine

14 Nov 2025

·endpoints.news

Merck to buy Cidara and its preventive influenza biologic for $9.2B

Merck said Friday it is buying Cidara Therapeutics in a deal worth $9.2 billion, centered around the biotech’s late-stage preventive antiviral biologic for seasonal influenza. The large pharma will pay $221.50 per share in cash, and the deal is expected to close in the first quarter of next year. The deal value represents a threefold boost over Cidara’s market cap of $3.3 billion when trading closed Thursday. Johnson & Johnson was previously working with Cidara on the antiviral, named CD388, in a deal that featured $27 million upfront. In 2024, Cidara took back the rights to the candidate. Observers have been keeping a close eye on how Merck would bolster its pipeline in the face of the upcoming patent cliff for Keytruda. Merck CEO Rob Davis told analysts during its third-quarter earnings call in October that it is reviewing how it can bolster its portfolio “ with urgency .” And it appears Merck may have a penchant for respiratory assets. Earlier this year, Merck bought Verona Pharma for its pulmonary disease therapies in a deal worth $10 billion. On Thursday, before the Cidara deal was announced, the Financial Times reported that a bidding war ensued for the biotech. This is a stark contrast to Merck’s move on Verona, where the large drugmaker was its only bidder . It is, however, reminiscent of the recently concluded contest between Novo Nordisk and Pfizer for the obesity biotech Metsera. Also on Friday, another bidding war started for the sleep biotech Avadel Pharmaceuticals between Alkermes and Lundbeck. Cidara, when reporting its earnings earlier this month, said its Phase 3 trial of CD388 is forecast to meet its 6,000-participant target by December. The study is recruiting healthy adults aged 65 years and over, as well as participants aged 12 years or older who are immunocompromised or at high risk of comorbidities. Interim data analysis is expected in Q1 next year. Last month, Cidara got an award from the US Biomedical Advanced Research and Development Authority (BARDA) worth up to $339 million to move the production of CD388 to the US and for further clinical research. CD388 features an Fc fragment of a human antibody that is conjugated with a small molecule inhibitor of viral neuraminidase. The biotech’s other assets are yet to enter the clinic. CBO421, which is in an IND-enabling stage, is designed to target CD75 for solid tumors. There are also two preclinical cancer assets, targeting CD73/PD-1 and CCR5, respectively.

AcquisitionPhase 3

14 Nov 2025

·www.pharmaceutical-technology.com

MSD bets big on flu antivirals with $9.2bn buyout of Cidara

Unlike vaccines, Cidara’s products do not rely on the immune system. Credit: Andy Dean Photography via Shutterstock.com. MSD has agreed to acquire Cidara Therapeutics in a $9.2bn deal, adding a new long-lasting infectious disease drug technology to its pipeline. The big pharma company will pay $221.50 per share in cash to buy Cidara, a US biotech that has developed a platform of drug-Fc conjugates (DFCs). The technology has allowed Cidara to build molecules with prolonged half-life whose efficacy does not require an immune response. This means that unlike traditional vaccines, Cidara’s products do not rely on the immune system. The biotech’s lead asset is CD388, a small molecule neuraminidase inhibitor linked to an Fc fragment of a human antibody designed to prevent influenza A and B. In an interview with Pharmaceutical Technology in October, Cidara’s CEO Jeff Stein said: “We turned a very potent enzyme inhibitor with poor drug properties into a great enzyme inhibitor with great drug properties. With those properties, it can be administered once per flu season.” CD388 is currently being evaluated in the Phase III ANCHOR study (NCT07159763) in adult and adolescent participants who are at higher risk of developing complications from influenza. The antiviral demonstrated success in the Phase IIb NAVIGATE study (NCT06609460), which helped it gain breakthrough therapy designation from the US Food and Drug Administration (FDA). MSD Research Laboratories president Dr Dean Li said: “This acquisition expands and complements our respiratory portfolio and pipeline.” GlobalData Strategic Intelligence US Tariffs are shifting - will you react or anticipate? Don’t let policy changes catch you off guard. Stay proactive with real-time data and expert analysis. By GlobalData Learn more about Strategic Intelligence For MSD, the acquisition of Cidara and CD388 looks set to add a strong growth avenue in the infectious disease sector. The buyout of a biotech developing antiviral drugs is even more significant given the modality’s distinction from vaccines, which have experienced volatility in the US under the Trump administration. MSD CEO Robert Davis said: “We intend to build on the Cidara team’s remarkable progress and are confident that CD388 has the potential to be another important driver of growth through the next decade, creating real value for shareholders.” The US Government has already seen the promise of Cidara’s technology, having awarded the biotech a hefty $339m funding award via the Biomedical Advanced Research and Development Authority (BARDA). The federal funding will be used to support domestic manufacturing of CD388 in the US and help establish an initial supply chain for commercialisation. The long-lasting nature of CD388 confers several advantages over vaccines in national efforts to fight seasonal viruses such as influenza. Stein added: “The most meaningful advantage is that we don’t have to change the manufacturing process from year to year, right in response to a changing influenza virus. “CD388 should be immune to any of that. It’s a single manufacturing process that is going to be unchanged. From a sheer economic perspective, it’s going to be much more feasible to stockpile a drug like CD388.” For MSD, the Cidara acquisition represents another billion-dollar deal in 2025. In July, the drugmaker agreed to acquire cardio-pulmonary specialist Verona Pharmaceuticals for $10bn. MSD is looking to shore up its pipeline as the loss of exclusivity for blockbuster cancer drug Keytruda (pembrolizumab) approaches. The company recently gained approval for a subcutaneous version oif the drug but analysts are uncertain about its chances on the market. Reacting to the Cidara acquisition, Citi analysts said in a research note: “Building upon the Verona acquisition, we believe this deal makes strategic sense as Cidara would build upon the respiratory portfolio with the phase III lead asset, CD388, designed to prevent influenza A and B, but we note the flu/ vaccine landscape may be challenging given regulatory uncertainty. “We note multiple deals may be necessary to offset loss of exclusivity exposure.” Pharmaceutical Technology Excellence Awards - The Benefits of Entering Gain the recognition you deserve! The Pharmaceutical Technology Excellence Awards celebrate innovation, leadership, and impact. By entering, you showcase your achievements, elevate your industry profile, and position yourself among top leaders driving pharmaceutical advancements. Don’t miss your chance to stand out—submit your entry today! Nominate Now

AcquisitionVaccinePhase 2Breakthrough TherapyPhase 3

100 Deals associated with CD-388

R&D Status

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Indication	Highest Phase	Country/Location	Organization	Date
Influenza, Human	Phase 3	United States	Cidara Therapeutics, Inc.	25 Sep 2025
Influenza, Human	Phase 3	United Kingdom	Cidara Therapeutics, Inc.	25 Sep 2025

Clinical Result

Indication

Phase

Evaluation

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Study	Phase	Population	Analyzed Enrollment	Group	Results	Evaluation	Publication Date


NCT05523089 (Pubmed \| Clin Infect Dis)	Phase 2	Influenza, Human	56	CD388 150 mg	zygyjqsyep(yhigqwnfzs) = uajbjmpxnh oaefxtijuz (xqzyhixxju )	Positive	08 Oct 2025
				Placebo	zygyjqsyep(yhigqwnfzs) = jwtnmdkpsj oaefxtijuz (xqzyhixxju )
NCT06609460 (NAVIGATE, Company_Website) Manual	Phase 2	-	-	CD388 (150 mg)	novgywdthv(kjcxpkwggo) = vkmmvmzdjx lkaqktgmho (lkbruljeor ) Met View more	Positive	07 Oct 2025
				CD388 (300 mg)	novgywdthv(kjcxpkwggo) = rpgjfmmzue lkaqktgmho (lkbruljeor ) Met View more
NCT05619536 (CTgov)	Phase 1	-	28	Saline placebo+CD388 Injection (Cohort 1)	gokokunpmg(qgntkcmjgq) = kcegiuwihl pvfmystaya (mokfmxhacf, 0.776) View more	-	01 Oct 2024
				Saline placebo+CD388 Injection (Cohort 2)	gokokunpmg(qgntkcmjgq) = szrwfcdaec pvfmystaya (mokfmxhacf, 4.10) View more
NCT05523089 (CTgov)	Phase 2	Influenza, Human	59	placebo (Placebo)	xqubtjdbdv(kipcwinfvw) = mcunnccbyy frayepkabs (neqffdlnmp, 11.86) View more	-	05 Sep 2024
				CD388 (150 mg CD388)	xqubtjdbdv(kipcwinfvw) = kivddkdaot frayepkabs (neqffdlnmp, 8.01) View more

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