Antiviral Platform
The Cloudbreak antiviral platform is a fundamentally new approach to the fight against life-threatening infectious disease that provides potent antiviral activity and immune system engagement in a single molecule. Our lead Cloudbreak candidates are Antiviral Fc-Conjugates (AVCs) for the prevention and treatment of influenza. The Cloudbreak antiviral platform has enabled us to expand the development of AVCs to target other life-threatening viruses such as RSV, HIV and coronavirus, including SARS-CoV-2 (COVID-19).
Cloudbreak Antiviral Platform Overview
The Cloudbreak antiviral platform recognizes that most infectious disease results when a microbial pathogen is able to evade or overcome the host immune system. Our AVC candidates are designed to counter infection in two ways, by directly targeting and destroying invading pathogens and by focusing the immune system at the site of infection. In this way, AVC candidates are similar to certain cancer immunotherapies that unlock the potential of the immune system to destroy cancer cells.
Multimodal Mechanism of Action from a Single Molecule
Cloudbreak candidates targeting viral infections are called Antiviral Fc-Conjugates (AVCs), single molecules consisting of two distinct moieties with discrete, yet complementary mechanisms of action:
- Targeting Moiety (TM): Novel and highly potent small molecule that binds surface targets on the pathogen to directly destroy it and/or inhibit replication.
- Effector Moiety (EM): Fragment crystallizable (Fc) region of human IgG1 antibodies, which was selected to maximize engagement of the human immune system via Fc-gamma (Fcγ) receptors and for its long half-life.
AVCs not only mediate pathogen clearance through a multimodal mechanism of action but also have potential for months of activity with a single dose.
Cloudbreak AVC (Antiviral Fc Conjugate) Program Overview
Cidara is leveraging the Cloudbreak antiviral platform to develop multiple AVCs. Each AVC targets a life-threatening virus. Our AVC research and development programs include:
- Influenza
- HIV
- RSV
- Coronavirus
Cidara seeks to develop AVCs that provide direct, sustained antiviral effect as well as immune system engagement, for effective prevention and treatment of disease. This is a potentially transformative approach, distinct from current therapies. AVCs are not vaccines, small-molecule drugs, or monoclonal antibodies. AVCs are novel, Fc-conjugates designed for the following features:
- Multimodal mechanism of action: Potent, direct antiviral activity and immune system engagement
- Strong target binding: High affinity to an essential, conserved target on the virus surface
- Long duration of action: Months of protection from disease with a single dose
- Rapid onset: Rapid distribution to site of infection for treatment of disease
Antiviral Fc Conjugates (AVCs) for Influenza
Several potential advantages of AVCs for influenza include:
- Broad-Spectrum, Universal Coverage: Cloudbreak AVCs have demonstrated activity against pandemic and seasonal influenza A and B viruses, including resistant (e.g. oseltamivir-resistant H1N1) and strains with high pandemic potential (e.g. H5N1, H7N9)
- Superior Resistance Profile: AVCs may be less prone to viral resistance, by virtue of the AVC multimodal mechanism of action
- Protection for High-Risk Populations: Unlike vaccines, the potent intrinsic activity of the AVCs should provide antiviral protection independent of immune system status. Even in immune-compromised patients, AVCs can focus the existing immune system at the site of infection
- Seasonal and Pandemic Readiness: AVCs are well-suited for immediate and robust response to influenza challenges by providing rapid onset of protection and coverage of strains that may have been missed by the seasonal vaccine. Moreover, AVCs are not subject to the lengthy and unpredictable process of vaccine manufacturing
- Long Duration of Action: A single AVC dose may protect from influenza for an entire season
Cidara’s lead influenza AVC development candidate is CD377, currently in preclinical development.
Cloudbreak AVC Development Candidate CD377: Preclinical Highlights
5 mice per cohort CD377 dosed 2 hours post infection (SC)
Coverage
Coverage of influenza A and B, including drug resistant strains
Serial Passage versus H1N11
1. A/CA/072009 H1N1pdm
2. Active form of Xofluza (baloxavir) used
3. Active form of Tamiflu (oseltamivir) used
Resistance
Reduced resistance potential
CD377 demonstrates lower resistance potential than Tamiflu and Xofluza
Treatment initiated 72 HOURS post-infection
Efficacy
Potential expansion of the treatment window
Lethal mouse influenza model (H1N1: TX/36/91)
Long-acting prevention model
Single 1 mg/kg doses were fully protective vs H1N1 (above), A/Hong Kong/1/68 H3N2, and Influenza B (Malaysia)
Duration
Potential for long-term single dose protection
Single 1 mg/kg subcutaneous dose protects mice from pandemic H1N1 for a month
Efficacy in BALB/c Severe Combined ImmunoDeficient (SCID) mice
5 mice per cohort. CD377 (SC) and baloxavir (PO) dosing was initiated 2 hours post-infection (H1N1: A/Puerto Rico/8/34)
Vulnerable
Protection in severely immune compromised hosts
Single 0.3 mg/kg subcutaneous dose protects mice from H1N1 for over a month
Efficacious by multiple dosing routes
5 mice per cohort CD377 dosed 2 hours post infection
Administration
Efficacious by multiple dosing routes
Single 0.1 mg/kg intravenous (IV), intramuscular (IM) and subcutaneous (SC) doses afford equivalent protection (HIN1: A/California/07/2009/pdm)
Cloudbreak AVC Development Candidate CD377: Preclinical Highlights
Coverage
Coverage of influenza A and B, including drug resistant strains
5 mice per cohort CD377 dosed 2 hours post infection (SC)
Resistance
Reduced resistance potential
CD377 demonstrates lower resistance potential than Tamiflu and Xofluza
Serial Passage versus H1N11
1. A/CA/072009 H1N1pdm
2. Active form of Xofluza (baloxavir) used
3. Active form of Tamiflu (oseltamivir) used
Efficacy
Potential expansion of the treatment window
Lethal mouse influenza model (H1N1: TX/36/91)
Treatment initiated 72 HOURS post-infection
Duration
Potential for long-term single dose protection
Single 1 mg/kg subcutaneous dose protects mice from pandemic H1N1 for a month
Long-acting prevention model
Single 1 mg/kg doses were fully protective vs H1N1 (above), A/Hong Kong/1/68 H3N2, and Influenza B (Malaysia)
Vulnerable
Protection in severely immune compromised hosts
Single 0.3 mg/kg subcutaneous dose protects mice from H1N1 for over a month
Efficacy in BALB/c Severe Combined ImmunoDeficient (SCID) mice
5 mice per cohort. CD377 (SC) and baloxavir (PO) dosing was initiated 2 hours post-infection (H1N1: A/Puerto Rico/8/34)
Administration
Efficacious by multiple dosing routes
Single 0.1 mg/kg intravenous (IV), intramuscular (IM) and subcutaneous (SC) doses afford equivalent protection (HIN1: A/California/07/2009/pdm)
Efficacious by multiple dosing routes
5 mice per cohort CD377 dosed 2 hours post infection
Influenza Virus
Influenza, or flu, is a virus that causes upper respiratory infection. The influenza virus can cause mild to severe illness, and at times can lead to influenza-related death. Young children, the elderly (people aged > 65 years and older), pregnant women, and immunocompromised patients are at higher risk of serious complications resulting from influenza infection, but even healthy people are at risk of infection with seasonal flu.
As many as 646,000 people may die from influenza-related illness each year worldwide. The annual burden of influenza in the U.S. results in approximately one million hospitalizations and emergency department visits and up to $11.7 billion in medical costs, with an additional $13.6 billion per year in lost earnings.
For the 2017-2018 season, the CDC estimates almost 50 million people in the U.S. became ill from influenza and almost 80,000 people died, making it one of the most severe seasons in recent history.
Prevention
Currently, the only preventive measure against influenza for most people is the seasonal influenza vaccine. While the influenza vaccine is critical to global health, it has limited vaccine effectiveness (VE) and must be redesigned every year based on a prediction for the next season’s dominant circulating strains. In recent years, the VE has varied significantly, with an average 40%. Even if not fully protective, vaccination reduces severity and influenza-related complications. Nevertheless, low VE results in more patients who are at risk of serious complications resulting from influenza and who must rely on a limited number of therapeutic options.
Treatment
Currently, four drugs for treating influenza are recommended by the CDC:
- Oseltamivir phosphate (Tamiflu®)
- Zanamivir (Relenza®)
- Peramivir (Rapivab®)
- Baloxavir marboxil (Xofluza™)
These drugs include neuraminidase inhibitors and the recently approved endonuclease inhibitor, baloxavir. All of these drugs have one or more of the following limitations: short half-life, high susceptibility to resistance, multi-dose regimens, and limited routes of administration.
Older antiviral medications, such as amantadine and rimantadine, are no longer recommended due to high levels of resistance.
For more information about influenza, visit the CDC website here.