Clinical Trials of Vaccines for Respiratory Syncytial Virus and Related Viruses

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications, trials & patents

Abstract

The LID is developing live attenuated vaccines against RSV, HPIV3, HMPV, HPIV1, and HPIV2 (in decreasing order of importance). Our emphasis is on RSV, although we have clinical studies in progress for most of these viruses. These vaccines are developed and produced from cloned cDNAs using reverse genetic systems of our making and employ defined attenuating mutations of our making. We develop candidates in pre-clinical studies and prepare vaccine seeds. Vaccine manufacture is performed under contact under our supervision, and clinical evaluation is performed by contract or collaboration under our supervision. Vaccines are evaluated clinically beginning in adults (who are seropositive for these common viruses), and moving successively to seropositive older children (typically 12-59 months of age) followed by seronegative younger children and infants (typically 6 -24 months of age for RSV, 6-59 months of age for the others). For RSV and HPIV3, viruses may be evaluated further in virus-naive young infants 1-3 months of age. Adult studies are open-label, whereas pediatric studies are double-blind placebo-controlled with a 2:1 ratio of vaccine to placebo recipients. For all RSV studies, subjects are followed during the subsequent RSV season (Nov 01 March 31) following the experimental immunization in order to assess the longevity of the antibody response and the rate and severity of natural RSV infection (although these studies are too small to reliably assess protective efficacy), and to confirm the absence of enhanced RSV disease. Since 2006, these clinical development activities have been supported in part by a CRADA with MedImmune. RSV vaccine: RSV has two antigenic subgroups, A and B, that have extensive cross-reactivity and cross-protection. We presently are focusing on RSV-A, the more important of the two. A subgroup A-based RSV vaccine may prove to be sufficiently cross-protective against RSV-B. If not, an RSV-B-based candidate can be developed based on the results with RSV-A. We previously made an RSV vaccine candidate called RSV delM2-2 that is based on deletion of the ORF encoding the M2-2 protein. This mutation provides up-regulation of antigen synthesis that may increase immunogenicity. In addition, deletion of a gene or ORF should be refractory to reversion or compensation, thus providing increased genetic and phenotypic stability. We have been conducting a phase I clinical study (NCT01459198) of a version of this mutant whose seed virus was supplied by MedImmune and is called RSV MEDI delM2-2. This candidate was highly restricted and well tolerated in adults and seropositive children. We have just completed evaluation in 30 seronegative children 6-24 months of age, and data analysis is still in progress. The vaccine appeared to induce reasonably strong antibody responses. The subjects in this study happened to have an unusually high incidence of adventitious infections by other respiratory viruses during the study period, which confounded evaluation of tolerability. Therefore, we are initiating a second phase 1 study in 51 additional seronegative children 6-24 months of age (NCT02040831), which is expected to begin in 2014. This study will use a version of the delM2-2 virus that was derived in our laboratory and is called RSV LID delM2-2. Part of this study will be done in collaboration with the International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Group. We previously developed another RSV candidate called RSV cps2 that contains a series of point mutations and deletion of the SH gene, and which is highly temperature-sensitive. RSV cps2 is presently in a phase I study in seronegative children 6-24 months of age (NCT01852266). This study involves 51 subjects; enrollment is expected to be completed in July, 2014, and the RSV surveillance period will be completed in March, 2015. Part of this study is being done with IMPAACT. We also previously developed another RSV vaccine candidate called RSV delNS2del1313. This virus contains the deletion of the nonstructural protein-2 (NS2) gene, which encodes a protein that antagonizes host responses to viral infection, notably the type I interferon (IFN) response. It also contains deletion of codon 1313 in the polymerase L protein. This virus was shown to be suitably attenuated in seropositive children 12-59 months of age, and presently is being evaluated in 30 seronegative children 6-24 months of age (NCT01893554). Enrollment is underway (as of July 2014). Thus, we have three promising RSV platforms in or entering phase I studies: delM2-2 (two versions), RSV cps2, and RSV delNS2del1313. These viruses have different properties (such as temperature-sensitivity and differences in antigen expression) and different mechanisms of attenuation (involving effects on RNA synthesis, regulation of RNA synthesis, IFN antagonism, among others). Our goal is to expeditiously identify a suitable live attenuated RSV candidate to bring forward into larger studies. HPIV3 vaccine: We have completed phase I evaluation of an attenuated version of HPIV3 called rHPIV3cp45. This is a recombinant version of a biologically derived cold-passaged (cp) virus that previously had been shown by LID and collaborators to exhibit satisfactory infectivity, safety, immunogenicity, and lack of transmissibility in seronegative infants and children in phase I and II studies. LID re-derived this virus from cDNA to provide a known pedigree for safety reasons. This virus was evaluated in a phase I clinical study in seronegative children 6-36 months of age in which two doses were given at a 6-month interval to investigate the durability of immunity and the feasibility of boosting at this interval (NCT01021397). Part of this study was done as companion protocols through Seattle Children's Hospital and IMPAACT. The results confirmed the equivalence of the cDNA-derived material with the previously-studied biologically-derived material. In addition, the results showed that the second dose induced an immune response in the few individuals who did not have a response to the first dose, and it boosted immunity in those who had a suboptimal response to the first dose. This is an excellent HPIV3 vaccine candidate that can advance to larger studies. It also is available to be combined with an attenuated RSV vaccine to create a bivalent vaccine, and indeed we previously showed that such a combination was compatible with regard to tolerability, replication, and immunogenicity of the two components. HPIV1 vaccine: We previously developed an HPIV1 vaccine candidate called rHPIV1-C(R84G/del170)HN(T553A)L(Y942A) that includes mutations that were engineered for genetic stability. Evaluation in adults and seropositive children 15 to 59 months of age showed that this candidate is highly attenuated. A phase I study in seronegative children 6 to 59 months of age (NCT00641017) showed that this virus is over-attenuated. These results provide a benchmark between pre-clinical assays and replication in humans. Over-attenuation can be corrected by reverse genetics. HPIV2 vaccine: We previously developed an HPIV2 vaccine candidate called rHPIV2-V94(15C)/948L/1724 that includes stabilized mutations. This virus was highly attenuated in adults. Presently, it is being evaluated in a phase I study in seropositive children 15 to 59 months of age (NCT01139437). HMPV vaccine: We previously developed an HMPV vaccine virus called rHMPV-Pa in which the HMPV P gene was replaced by that of avian MPV, thus conferring a host range attenuation phenotype. Evaluation in adults and seropositive children 15 to 59 months of age showed that it is highly attenuated. The vaccine is presently being evaluated in seronegative children 6-59 months of age (NCT01255410).