White paper on microbial anti-cancer therapy and prevention.

In this White Paper, we discuss the current state of microbial cancer therapy. This paper resulted from a meeting ('Microbial Based Cancer Therapy') at the US National Cancer Institute in the summer of 2017. Here, we define 'Microbial Therapy' to include both oncolytic viral therapy and bacterial anticancer therapy. Both of these fields exploit tumor-specific infectious microbes to treat cancer, have similar mechanisms of action, and are facing similar challenges to commercialization. We designed this paper to nucleate this growing field of microbial therapeutics and increase interactions between researchers in it and related fields. The authors of this paper include many primary researchers in this field. In this paper, we discuss the potential, status and opportunities for microbial therapy as well as strategies attempted to date and important questions that need to be addressed. The main areas that we think will have the greatest impact are immune stimulation, control of efficacy, control of delivery, and safety. There is much excitement about the potential of this field to treat currently intractable cancer. Much of the potential exists because these therapies utilize unique mechanisms of action, difficult to achieve with other biological or small molecule drugs. By better understanding and controlling these mechanisms, we will create new therapies that will become integral components of cancer care.

Attenuation of neurovirulence, biodistribution, and shedding of a poliovirus:rhinovirus chimera after intrathalamic inoculation in Macaca fascicularis.

A dependence of poliovirus on an unorthodox translation initiation mode can be targeted selectively to drive viral protein synthesis and cytotoxicity in malignant cells. Transformed cells are naturally susceptible to poliovirus, due to widespread ectopic upregulation of the poliovirus receptor, Necl-5, in ectodermal/neuroectodermal cancers. Viral tumor cell killing and the host immunologic response it engenders produce potent, lasting antineoplastic effects in animal tumor models. Clinical application of this principle depends on unequivocal demonstration of safety in primate models for paralytic poliomyelitis. We conducted extensive dose-range-finding, toxicity, biodistribution, shedding, and neutralizing antibody studies of the prototype oncolytic poliovirus recombinant, PVS-RIPO, after intrathalamic inoculation in Macaca fascicularis. These studies suggest that intracerebral PVS-RIPO inoculation does not lead to viral propagation in the central nervous system (CNS), does not cause histopathological CNS lesions or neurological symptoms that can be attributed to the virus, is not associated with extraneural virus dissemination or replication and does not induce shedding of virus with stool. Intrathalamic PVS-RIPO inoculation induced neutralizing antibody responses against poliovirus serotype 1 in all animals studied.

Regulatory aspects for translating gene therapy research into the clinic.

Gene therapy products are highly regulated, therefore moving a promising candidate from the laboratory into the clinic can present unique challenges. Success can only be achieved by proper planning and communication within the clinical development team, as well as consultation with the regulatory scientists who will eventually review the clinical plan. Regulators should not be considered as obstacles but rather as collaborators whose advice can significantly expedite the product development. Sound scientific data is required and reviewed by the regulatory agencies to determine whether the potential benefit to the patient population outweighs the risk. Therefore, compliance with Good Manufacturing Practice (GMP) and Good Laboratory Practice (GLP) principles to ensure quality, safety, purity, and potency of the product, and to establish "proof of concept" for efficacy, and for safety information, respectively, is essential. The design and conduct of the clinical trial must adhere to Good Clinical Practice (GCP) principals. The clinical protocol should contain adequate rationale, supported by nonclinical data, to justify the starting dose and regimen, and adequate safety monitoring based on the patient population and the anticipated toxicities. Proper review and approval of gene therapy clinical studies by numerous committees, and regulatory agencies before and throughout the study allows for ongoing risk assessment of these novel and innovative products. The ethical conduct of clinical trials must be a priority for all clinical investigators and sponsors. As history has shown us, only a few fatal mistakes can dramatically alter the regulation of investigational products for all individuals involved in gene therapy clinical research, and further delay the advancement of gene therapy to licensed medicinal products.