IL-2 plasmid electroporation: from preclinical studies to phase I clinical trial.

Electroporation (EP)-assisted intralesional delivery of Interleukin-2 (IL-2) plasmid (pDNA) has the potential to increase the local concentration of the expressed cytokine for an extended time in the injected tumors while minimizing its systemic concentration, in comparison with systemic delivery of the recombinant cytokine. Nonclinical Investigational New Drug application-enabling studies were performed in mice to evaluate the effect of intratumoral administration of murine IL-2 pDNA on local expression and systemic distribution of IL-2 transgene as well as the inhibition of established tumor growth. The safety of repeated administrations of a human IL-2 pDNA product candidate with EP was evaluated in rats. Following the nonclinical safety and efficacy studies, a human IL-2 pDNA product candidate intralesionally administered with EP to metastatic melanoma patients is currently being investigated in a phase I clinical trial.

Clinical Development of a Cytomegalovirus DNA Vaccine: From Product Concept to Pivotal Phase 3 Trial.

2013 marks a milestone year for plasmid DNA vaccine development as a first-in-class cytomegalovirus (CMV) DNA vaccine enters pivotal phase 3 testing. This vaccine consists of two plasmids expressing CMV antigens glycoprotein B (gB) and phosphoprotein 65 (pp65) formulated with a CRL1005 poloxamer and benzalkonium chloride (BAK) delivery system designed to enhance plasmid expression. The vaccine's planned initial indication under investigation is for prevention of CMV reactivation in CMV-seropositive (CMV⁺) recipients of an allogeneic hematopoietic stem cell transplant (HCT). A randomized, double-blind placebo-controlled phase 2 proof-of-concept study provided initial evidence of the safety of this product in CMV⁺ HCT recipients who underwent immune ablation conditioning regimens. This study revealed a significant reduction in viral load endpoints and increased frequencies of pp65-specific interferon-γ-producing T cells in vaccine recipients compared to placebo recipients. The results of this endpoint-defining trial provided the basis for defining the primary and secondary endpoints of a global phase 3 trial in HCT recipients. A case study is presented here describing the development history of this vaccine from product concept to initiation of the phase 3 trial.

A novel therapeutic cytomegalovirus DNA vaccine in allogeneic haemopoietic stem-cell transplantation: a randomised, double-blind, placebo-controlled, phase 2 trial.

BACKGROUND: Cytomegalovirus reactivation occurs within 6 months in 60-70% of cytomegalovirus-seropositive patients after allogeneic haemopoietic stem-cell transplantation (HSCT), mainly due to immunosuppression associated with the procedure. Pre-emptive antiviral therapy reduces incidence of cytomegalovirus disease but can be toxic. To reduce the potential for disease and subsequent need for such antiviral drugs, we aimed to assess safety and efficacy of a cytomegalovirus therapeutic DNA vaccine compared with placebo. METHODS: In this exploratory double-blind, placebo-controlled, parallel group, phase 2 trial, up to 80 donor-recipient pairs and 80 unpaired recipients undergoing allogeneic HSCT were planned for enrolment at 16 transplant centres in the USA. Eligible recipients were cytomegalovirus-seropositive, 18-65 years old, without high-risk primary disease, T-cell depletion, previous vaccination for cytomegalovirus, or autoimmune diseases. We randomly allocated participants in both parallel groups in a 1:1 ratio to receive a cytomegalovirus therapeutic DNA vaccine (TransVax; Vical, San Diego, CA, USA) or placebo before conditioning and at 1, 3, and 6 months after transplantation. The vaccine contains plasmids encoding cytomegalovirus glycoprotein B and phosphoprotein 65 formulated with poloxamer CRL1005 and benzalkonium chloride. Randomisation was done by sequential allocation based on Pocock and Simon's method, and stratified by site, donor-recipient HLA matching status, and donor's cytomegalovirus serostatus. The primary outcome was the occurrence rate of clinically significant viraemia resulting in initiation of cytomegalovirus-specific antiviral therapy in the per-protocol assessable population. We assessed rates of adverse events in all participants who received at least one dose of vaccine or placebo. This study is registered with ClinicalTrials.gov, number NCT00285259. FINDINGS: We randomly allocated 108 participants (94 HSCT recipients and 14 paired donors) between June 29, 2006, and Dec 11, 2009. Enrolment of the paired arm was halted in February 2008 for logistical reasons. Safety was assessed in all participants; the efficacy population was restricted to 74 unpaired recipients. Groups were balanced for demographic and clinical variables. 19 (48%) of 40 vaccine recipients required cytomegalovirus-specific antiviral therapy, compared with 21 (62%) of 34 controls (p=0·145). However, during follow-up vaccine significantly reduced the occurrence and recurrence of cytomegalovirus viraemia and improved the time-to-event for viraemia episodes compared with placebo. The vaccine was well-tolerated; only one participant discontinued after an allergic reaction. Incidence of common adverse events after HSCT (eg, graft-versus-host disease or secondary infections) did not differ between groups. INTERPRETATION: We show proof of concept for an immunotherapeutic cytomegalovirus vaccine (TransVax) for clinically significant viraemia in the HSCT setting. The reported safety and efficacy outcomes support further development in a phase 3 trial, notwithstanding a lack of significant reduction in the use of cytomegalovirus-specific antiviral therapy compared with placebo in this phase 2 trial. FUNDING: Vical and US National Institute of Allergy and Infectious Diseases.

Phase 1 clinical trials of the safety and immunogenicity of adjuvanted plasmid DNA vaccines encoding influenza A virus H5 hemagglutinin.

BACKGROUND: Development of vaccines against highly pathogenic avian influenza virus H5N1 subtypes posing a pandemic threat remains a priority. Limitations in manufacturing capacity and production time of conventional inactivated vaccines highlight the need for additional approaches. METHODS: We conducted two double-blind, placebo-controlled phase 1 studies involving a total of 103 healthy adults who received two intramuscular injections of Vaxfectin-adjuvanted plasmid DNA vaccine or placebo 21 days apart. Vaccine cohorts received either a monovalent vaccine containing an A/Vietnam/1203/04 H5 hemagglutinin-encoding plasmid or a trivalent vaccine with plasmids encoding H5, NP, and M2 proteins in doses from 0.1 to 1mg of DNA/injection. RESULTS: All doses were well tolerated without vaccine-related serious adverse events or discontinuations. In the monovalent cohorts, hemagglutination inhibition (HI) titers of > or =40 and 4-fold rises from baseline were achieved in 47-67% of subjects and H5-specific T-cell responses in 75-100%. Trivalent cohorts had lower HI response rates (< or = 20%), but 72% of subjects achieved T-cell and/or antibody responses to one or more antigens. CONCLUSIONS: Vaxfectin-adjuvanted monovalent H5 DNA vaccines were well tolerated and induced HI response rates and titers in the reported range of inactivated protein-based H5 vaccines, suggesting that adjuvanted DNA vaccines with rapid vaccine production could be useful for pandemic control.

Comparison of rabbit and mouse models for persistence analysis of plasmid-based vaccines.

Experiments were conducted with a cationic lipid-formulated pDNA vaccine (VCL-AB01) to evaluate the models used to determine biodistribution, persistence and the potential for integration (into genomic DNA) of plasmid DNA-based vaccines. Mice were injected with a high-dose volume of 50 microL unilaterally containing approximately 1.33 x 10(13) plasmid copy numbers (PCN) or a low-dose volume of 20 microL bilaterally ( approximately 5.3 x 10(12) PCN). Rabbits were injected bilaterally with a 0.5 mL ( approximately 1.33 x 10(14) PCN) volume. Injection site muscle tissue was harvested two days, one month, and two months postinjection for the low-dose murine and rabbit models and two days and two months postinjection for the high-dose murine model. Total DNA was extracted and analyzed by real-time quantitative PCR for sequences specific to the injected pDNA. The geometric mean PCN/microg of total DNA from the high and low dose models were compared to determine if injection volume impacts clearance and/or persistence. Results from these studies showed that PCN clearance over two months was similar in mice injected with 20 microL and rabbits injected with 0.5 mL, but PCN clearance was slower in mice injected with similar PCN in 50 microL (1.33 x 10(13) PCN) compared to 20 microL (5.3 x 10(12) PCN). Persistence at two months in the rabbit and low-dose murine models was comparable, with geometric mean of 5.22 x 10(3) PCN/microg of total DNA for the low-dose volume murine model and 2.81 x 10(3)/microg DNA for the rabbit model. Interanimal variability in persistence was not impacted by dose volume.