GeoVax (United States)

Abstract The project pursues clinical testing of a gene-based treatment for refractory malignancy of the head and neck. Background We are evaluating intratumoral nucleoside cleavage by E. coli purine nucleoside phosphorylase (PNP) as an experimental therapy for refractory solid tumors. The approach requires delivery of PNP transgene to tumor parenchyma followed by prodrug administration, and provides “bystander” killing by a very potent purine antimetabolite (F-Ade) generated intratumorally. F-Ade is 1,000-times more potent than fluorouracil, the chemotherapeutic produced by cytosine deaminase (CD; a first-generation construct used for tumor sensitization). PNP/F-Ade has been found to be superior to CD/fluorouracil by several laboratories. In a Phase 1 study (Rosenthal et al., Ann. Oncol.), antitumor activity was observed after IT injections of a recombinant adenovirus encoding PNP (Ad/PNP), followed by IV fludarabine phosphate (F-araAMP, a prodrug converted by PNP to F-Ade). Methods Patients in the present trial have RECIST 1.1 measurable HNSCC amenable to local injection and no other palliative treatment options. A single-arm protocol is being used to evaluate safety of repeat cycles of Ad/PNP and F-araAMP. Ad/PNP is injected intratumorally twice on Day 1 and once on Day 2, followed by infusion of F-araAMP on Days 3, 4, and 5 every 4 weeks for up to 5 cycles. Results Eight patients have been enrolled to date. There have been no dose limiting toxicities, no serious adverse events (SAEs) definitively attributable to treatment, and no AEs above grade 3 severity. Up to five cycles of Ad/PNP treatment have been administered without limiting sequelae. Intratumoral expression of PNP transgene by RT-PCR has been established in treated tumors. Other correlative endpoints are in process and will be discussed. One patient exhibited tumor volume reduction by approximately 21% (as judged by CT imaging) and did not increase during five months of treatment, consistent with clinically stable disease. Two other patients completed three months of Ad/PNP with stable disease by RECIST criteria during the treatment period. Another patient’s tumor (largest dimension 3.1 cm) demonstrated 25% decrease after one treatment cycle. Challenges have included: 1) complexity of distribution of agent into large volume tumors (e.g., >100 ml) with small volume of Ad/PNP, and 2) acute swelling of tumor tissue following intratumoral virus injection in two patients, consistent with inflammatory response and/or disease progression. Conclusions Administration of Ad/PNP is safe and feasible. Injections of large volume tumors remains a challenge. The strategy is also being considered for earlier-stage HNSCC with less tumor burden, including a role similar to neoadjuvant or cytoreductive radiotherapy in combination with checkpoint blockade inhibition. A muti-center trial is planned to define MTD and feasibility in smaller tumors. Citation Format: A. Dimitrios Colevas, Eric J. Sorscher, William B. Parker, Roan Courtney Raymundo, Jeong S. Hong, Regina Rab, Camilo Henao, Nikki Schmitt, Madison Stallings, Kelly T. McKee, Eben Rosenthal, Joseph Curry. Phase 1/2 study of Ad/PNP with fludarabine for the treatment of head & neck squamous cell carcinoma (HNSCC) [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-005.

Lassa fever surpasses Ebola, Marburg, and all other hemorrhagic fevers except Dengue in its public health impact. Caused by Lassa virus (LASV), the disease is a scourge on populations in endemic areas of West Africa, where reported incidence is higher. Here, we report construction, characterization, and preclinical efficacy of a novel recombinant vaccine candidate GEO-LM01. Constructed in the Modified Vaccinia Ankara (MVA) vector, GEO-LM01 expresses the glycoprotein precursor (GPC) and zinc-binding matrix protein (Z) from the prototype Josiah strain lineage IV. When expressed together, GP and Z form Virus-Like Particles (VLPs) in cell culture. Immunogenicity and efficacy of GEO-LM01 was tested in a mouse challenge model. A single intramuscular dose of GEO-LM01 protected 100% of CBA/J mice challenged with a lethal dose of ML29, a Mopeia/Lassa reassortant virus, delivered directly into the brain. In contrast, all control animals died within one week. The vaccine induced low levels of antibodies but Lassa-specific CD4+ and CD8+ T cell responses. This is the first report showing that a single dose of a replication-deficient MVA vector can confer full protection against a lethal challenge with ML29 virus.

It remains a challenge to develop a successful human immunodeficiency virus (HIV) vaccine that is capable of preventing infection. Here, we utilized the benefits of CD40L, a costimulatory molecule that can stimulate both dendritic cells (DCs) and B cells, as an adjuvant for our simian immunodeficiency virus (SIV) DNA vaccine in rhesus macaques. We coexpressed the CD40L with our DNA/SIV vaccine such that the CD40L is anchored on the membrane of SIV virus-like particle (VLP). These CD40L containing SIV VLPs showed enhanced activation of DCs in vitro. We then tested the potential of DNA/SIV-CD40L vaccine to adjuvant the DNA prime of a DNA/modified vaccinia virus Ankara (MVA) vaccine in rhesus macaques. Our results demonstrated that the CD40L adjuvant enhanced the functional quality of anti-Env antibody response and breadth of anti-SIV CD8 and CD4 T cell responses, significantly delayed the acquisition of heterologous mucosal SIV infection, and improved viral control. Notably, the CD40L adjuvant enhanced the control of viral replication in the gut at the site of challenge that was associated with lower mucosal CD8 immune activation, one of the strong predictors of disease progression. Collectively, our results highlight the benefits of CD40L adjuvant for enhancing antiviral humoral and cellular immunity, leading to enhanced protection against a pathogenic SIV. A single adjuvant that enhances both humoral and cellular immunity is rare and thus underlines the importance and practicality of CD40L as an adjuvant for vaccines against infectious diseases, including HIV-1. Despite many advances in the field of AIDS research, an effective AIDS vaccine that can prevent infection remains elusive. CD40L is a key stimulator of dendritic cells and B cells and can therefore enhance T cell and antibody responses, but its overly potent nature can lead to adverse effects unless used in small doses. In order to modulate local expression of CD40L at relatively lower levels, we expressed CD40L in a membrane-bound form, along with SIV antigens, in a nucleic acid (DNA) vector. We tested the immunogenicity and efficacy of the CD40L-adjuvanted vaccine in macaques using a heterologous mucosal SIV infection. The CD40L-adjuvanted vaccine enhanced the functional quality of anti-Env antibody response and breadth of anti-SIV T cell responses and improved protection. These results demonstrate that VLP-membrane-bound CD40L serves as a novel adjuvant for an HIV vaccine.

We have previously shown that macaques vaccinated with DNA vectors expressing SIVmac239 antigens developed potent immune responses able to reduce viremia upon high-dose SIVmac251 challenge. To further improve vaccine-induced immunity and protection, we combined the SIVmac239 DNA vaccine with protein immunization using inactivated SIVmac239 viral particles as protein source. Twenty-six weeks after the last vaccination, the animals were challenged intrarectally at weekly intervals with a titrated dose of the heterologous SIVsmE660. Two of DNA-protein coimmunized macaques did not become infected after 14 challenges, but all controls were infected by 11 challenges. Vaccinated macaques showed modest protection from SIVsmE660 acquisition compared with naïve controls (P = 0.050; stratified for TRIM5α genotype). Vaccinees had significantly lower peak (1.6 log, P = 0.0048) and chronic phase viremia (P = 0.044), with 73% of the vaccinees suppressing viral replication to levels below assay detection during the 40-wk follow-up. Vaccine-induced immune responses associated significantly with virus control: binding antibody titers and the presence of rectal IgG to SIVsmE660 Env correlated with delayed SIVsmE660 acquisition; SIV-specific cytotoxic T cells, prechallenge CD4(+) effector memory, and postchallenge CD8(+) transitional memory cells correlated with control of viremia. Thus, SIVmac239 DNA and protein-based vaccine protocols were able to achieve high, persistent, broad, and effective cellular and humoral immune responses able to delay heterologous SIVsmE660 infection and to provide long-term control of viremia. These studies support a role of DNA and protein-based vaccines for development of an efficacious HIV/AIDS vaccine.

The GeoVax DNA and MVA-vectored HIV vaccines are single recombinant moieties designed to express non-infectious, immature virus-like-particles bearing “native” Env protein. The DNA vaccines encode Gag, Pol and Env using HIV subgenomic splicing, with or without GM-CSF in the nef region, while the MVA vectored vaccines encode Gag, Pol and Env under the control of the mH5 early/late vaccinia promoter. This vaccine design was tested using the rhesus macaque model and SIV-239 prototype vaccines encoding the analogous SIV structural proteins, with and without GM-CSF. A heterologous (DNA + MVA) vaccination regimen was employed with standard immune response measurements and efficacy testing using weekly intra-rectal heterologous infectious challenges with SIV-E660 (MID40). Comparable cellular immune responses were induced. However, the GM-CSF-supplemented vaccine induced antibodies specific to SIV gp160 with higher binding avidity to the “native” protein and higher neutralization titers specific for a tier 1 variant of E660 (E660.11). The GM-CSF supplemented vaccine also induced a higher level of efficacy with 70% (5/7) of the animals protected against 12 challenges; compared to a 25% (2/8) level of efficacy obtained using the unadjuvanted vaccine. The use of the MVA vectored SIV vaccine alone, without GM-CSF, induced higher titers of antibodies specific to SIV gp160 and reduced cellular responses. The level of protection was comparable, if not better, to that obtained using the unadjuvanted DNA + MVA products. In a completed Phase 1 (HVTN-065) clinical trial, similar immune response patterns were observed with the administration of the MVA vectored vaccine alone resulting in higher titers of antibodies while the use of the heterologous prime-boost regimen DNA + MVA induced higher CD4+ T cell responses and lower antibody titers. The unadjuvanted HIV vaccines are currently being tested in a Phase 2 trial (HVTN-205) while the GM-CSF supplemented vaccine represents the next generation product in the GeoVax pipeline.

Methods Three groups of rhesus macaques, eight per group, were studied. The Dryvax-naive and Dryvax-immune groups received the DNA/MVA SIV vaccine (DNA at weeks 0 and 8, and rMVA at weeks 16 and 24). In addition, the Dryvaximmune group received the Dryvax vaccine 1.5 years prior to the DNA prime. The control group did not receive any vaccine. All macaques were challenged intrarectally with SIV251 at 9 months after the final MVA.

A less-virulent poliovirus generated by altering codon usage suggests a new strategy for vaccine development.