Ebola update: two therapeutic approaches show promise

BALTIMORE and PHILADELPHIA—Profectus BioSciences, Inc., a clinical-stage vaccine company developing novel vaccines for the treatment and prevention of infectious diseases, announced that the Department of Defense (DoD) through the Medical Countermeasure Systems-Joint Vaccine Acquisition Program (MCS-JVAP) has contracted the manufacture and IND-enabling preclinical testing of the Profectus trivalent Ebola/Marburg vaccine. In addition, Battelle Memorial Institute has been contracted for clinical evaluation of the VesiculoVax™ Zaire-Ebola virus vaccine to meet the current outbreak in West Africa. The $9.5 million award was made with Battelle which, in turn, has contracted with Profectus for manufacturing and clinical evaluation and with Charles River Laboratories and Biologics Consulting Group for preclinical testing and IND preparation, respectively.

“While the urgent need today is for a vaccine that protects against the current Ebola Zaire outbreak, we are also anticipating the needs for tomorrow. We are continuing to develop a trivalent vaccine that will protect our service members and DoD civilians against the major filovirus threats: Ebola Zaire, Ebola Sudan, and Marburg viruses,” said LTC Victor Suarez, MCS-JVAP joint product manager. “The available evidence suggests that a trivalent vaccine, such as the one under development by Profectus, is the desired end point as it would simultaneously offer protection against the current Ebola Zaire outbreak and also meet the long-term goals of preventing future infections by the Ebola Sudan and Marburg viruses. The DoD is optimistic that its long-term commitment to identifying and supporting safe and effective trivalent filovirus vaccines is coming to fruition and remains supportive to advancing the Profectus BioSciences trivalent Ebola/Marburg vaccine into human clinical trials as rapidly as possible.”

“We are gratified that the Department of Defense has recognized the potential of Profectus’ VesiculoVax Zaire-Ebola virus vaccine to combat the current outbreak in West Africa, and the potential of our multi-component vaccine to protect civilians and military personnel against all strains of filoviruses, whether from natural outbreak or deliberate misuse,” said John Eldridge, Ph.D., chief scientific officer of Profectus. “More than 15 years have been invested in developing the genetically attenuated rVSVN4CT1 VesiculoVax vaccine delivery platform and demonstrating its safety in multiple clinical trials. To date, it is the only vaccine to demonstrate single-dose protection of monkeys against lethal challenge with highly virulent low passage Ebola and Marburg viruses.”

Profectus began development of VesiculoVax rVSVN4CT1 vectored Ebola and Marburg vaccines approximately five years ago. The initial studies demonstrated that a single dose of the rVSVN4CT1-Z-Ebola vaccine protected guinea pigs and rhesus macaques against morbidity and mortality when challenged with a lethal dose of Zaire-Ebola virus.

Subsequently, Profectus provided rVSVN4CT1 vectored Ebola and Marburg vaccine candidates into studies conducted by the Filovirus Animal Non-clinical Group (FANG). This team includes members from the National Institute for Allergy and Infectious Diseases (NIAID), the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), and the U.S. Department of Defense (DoD), and is charged with identifying and filling knowledge gaps in the areas of assays, animal models, challenge material, and human clinical data in support of advanced development licensure studies for Ebola and Marburg vaccines. In the FANG studies a single dose of the Profectus VesiculoVax rVSVN4CT1-vectored Ebola vaccine provided 100 percent protection of non-human primates against challenge with 1,000 times the lethal dose of highly pathogenic low passage Zaire-Ebola virus. In addition, a single dose of the Profectus VesiculoVax rVSVN4CT1-vectored Marburg vaccine provided 100 percent protection against challenge with 1,000 times the lethal dose of low passage Angola-Marburg virus.

In October 2014, Profectus BioSciences was awarded a one-year $5.8M contract with BARDA to manufacture the company’s novel VesiculoVax Zaire-Ebola vaccine candidate for use in Phase 1 clinical studies. The contract can be extended to a total of 13 months and $8.6 million. Profectus will apply to the FDA for an Investigational New Drug (IND) designation that would allow initiation of human clinical trials of the vaccine’s safety and immunogenicity in humans.

This most recent contract award for $9.5M from the JVAP through Battelle will support manufacture of the trivalent rVSVN4CT-vectored Ebola/Marburg vaccine, and phase 1 clinical evaluation of rVSVN4CT1-Zaire-Ebola virus vaccine for safety and immunogenicity. A rapid follow-up trial of the trivalent vaccine is planned.

In a second development, Philadelphia-based Hemispherx Biopharma, Inc. continued to detail its progress through a new peer-reviewed publication entitled, “The Quest for Effective Ebola Treatment; Ebola VP35 is an Evidence-Based Target for dsRNA Drugs” in the Nature Group’s current issue of Emerging Microbes and Infections (October 29, 2014). This publication was authored by affiliates of Hemispherx. The publication provides an illustration of the crystallographic coordinates of a truncated VP35 complex with dsRNA.

As explained by Hemispherx, death from Ebola virus (EBOV) infection is associated with markedly impaired coagulation and innate immunity cascades, increased production of pro-inflammatory cytokines, profound immune suppression resulting in peripheral T lymphocyte apoptosis, and a lack of adaptive immunity (Fields Virology 923-956, 2013).

By contrast, survivors of infection develop an effective immune response with the production of EBOV neutralizing antibodies. Early events in EBOV infection influence the patient’s ability to develop an effective immune response. The success of EBOV replication is dependent on viral inhibition of initial innate immune responses to infection. Disarming innate immune responses is a common mechanism employed by highly pathogenic human viruses, including those of the influenza and coronavirus families (Antiviral Res 100:615, 2013). EBOV is one of the more successful of the emerging highly pathogenic viruses in evasion of innate immune mechanisms.

VP35 is a multifunctional major virulence protein that is indispensable for EBOV replication. Double-stranded RNA (dsRNA) is a necessary component of viral replication, which initiates systemic signaling cascades that normally activate interferon (IFN) regulatory factors leading to the production of IFN-α/β (type I IFNs). VP35 inhibition of dsRNA effectively disarms essential components of the innate immune response. VP35 binds to sequence-independent dsRNA, resulting in the suppression of multiple steps in the IFN signaling cascade, which otherwise would provide a broad antiviral state by activation of both the innate and adaptive arms of the immune response.

Multiple investigators have demonstrated that VP35 binds dsRNA (Antiviral Res 93:354, 2012) and molecular crystallographic analysis has demonstrated that binding is achieved by non-covalent bonding with the dsRNA phosphodiester backbone and thus shielding of viral produced dsRNA from host antiviral signaling pathways (Nat Struct Mol Biol 17:165, 2010). The unavailability of viral-produced dsRNA during replication results in an increased virus load and its consequences. Thus, the VP35-dsRNA interaction is an evidence-based target for antiviral interruption of EBOV, potentially ameliorating the pathogenesis of EVD, Hemispherx’ analysis concludes.

Therapeutic dsRNA may overcome the lethal dsRNA sequestration action of VP35 and reverse the “dsRNA deficiency” associated with Ebola. Various forms of dsRNA have been studied as inducers of type I IFNs and several derivatives have survived the rigors of animal and clinical testing. Poly I:Poly C₁₂U (rintatolimod, Ampligen®) was designed as an IFN inducer with a markedly reduced incidence of adverse events compared to the parent compound poly I:poly C and has demonstrated antiviral activity against a wide variety of DNA and RNA viruses in pre-clinical testing, including SARS (Severe Acute Respiratory Syndrome). Multiple mechanisms may be involved in the antiviral activity of rintatolimod in its predicted EBOV utility. These include direct induction of innate immunity as a TLR3 agonist, competition for VP35 binding with dsRNA allowing activation of innate immune responses, and/or serve as a required dsRNA cofactor for IFN-induced enzymes that function in the innate immune cascades triggered by viral infections.

In contrast to drugs under intensive development to help contain the global Ebola crisis, Hemispherx points out that sequestration of dsRNA is non-sequence dependent with the phosphodiester backbone freely available for VP35 binding. Since EBOV has been demonstrated to be mutating rapidly in this epidemic (Science 345:1369, 2014), anti-Ebola agents that depend on sequence maintenance (vaccines, monoclonal antibodies, active site viral enzyme inhibitors) may be at risk following clinical development even with crisis activated reductions in regulatory requirements.

In animal studies, Hemispherx’ Ampligen® was also efficacious by a second mechanism as an adjuvant for highly pathogenic avian influenza virus vaccines, and this drug is now being evaluated as an adjuvant in a variety of cancer vaccine trials. Epitope expansion has also been observed with Ampligen applied intranasally in man (Vaccine 32(42):5490, 2014) and this property may also result in antibody levels to accelerate recovery from Ebola and evade mutational inhibitory properties.

In third world countries, with limited facilities for medical intervention, protecting the individual from exposure to Ebola-containing bodily fluids may be achieved by heightening immunity on the majority of mucosal surfaces, as by the potential use of intranasal sprays of Ampligen®.

Hemispherx is working with regulatory authorities to potentially inhibit further escalation of the current Ebola crisis. On September 29, 2014, the company announced a series of collaborations designed to determine the potential effectiveness of Alferon® N and Ampligen® as potential preventative and/or therapeutic treatments for Ebola related disorders.