Immunogene therapy of human melanoma. Phase I/II clinical trial

Design of clinical trials for therapeutic cancer vaccines development

Advances in molecular and cellular biology as well as biotechnology led to definition of a group of drugs referred to as medicinal products of advanced technologies. It includes gene therapy products, somatic cell therapeutics and tissue engineering. Therapeutic cancer vaccines including whole cell tumor cells vaccines or gene modified whole cells belong to somatic therapeutics and/or gene therapy products category. The drug development is a multistep complex process. It comprises of two phases: preclinical and clinical. Guidelines on preclinical testing of cell based immunotherapy medicinal products have been defined by regulatory agencies and are available. However, clinical testing of therapeutic cancer vaccines is still under debate. It presents a serious problem since recently clinical efficacy of the number of cancer vaccines has been demonstrated that focused a lot of public attention. In general clinical testing in the current form is very expensive, time consuming and poorly designed what may lead to overlooking of products clinically beneficial for patients. Accordingly regulatory authorities and researches including Cancer Vaccine Clinical Trial Working Group proposed three regulatory solutions to facilitate clinical development of cancer vaccines: cost-recovery program, conditional marketing authorization, and a new development paradigm. Paradigm includes a model in which cancer vaccines are investigated in two types of clinical trials: proof-of-principle and efficacy. The proof-of-principle trial objectives are: safety; dose selection and schedule of vaccination; and demonstration of proof-of-principle. Efficacy trials are randomized clinical trials with objectives of demonstrating clinical benefit either directly or through a surrogate. The clinical end points are still under debate.

[Gene therapy of melanoma: review of published clinical trials]

INTRODUCTION

Melanoma frequency increases. Conventional antitumoral treatments fail. Gene therapy for metastatic melanoma is studied in 17 phase I-II clinical trials. ACTUALITES ET POINTS FORTS: Sixteen use cytokine genes. These studies are heterogenous as far as methodology is concerned. Gene therapy clinical tolerance is acceptable. Security is rarely discuted. In these studies overall response rate is 8%, with histological complete responses.

PERSPECTIVES

Presently, three new studies are opened in United States.

Advances in gene transfer into haematopoietic stem cells by adenoviral vectors

Until recently, the cells of haematopoietic origin were not considered good adenoviral (Adv) targets, primarily because they lacked the specific Adv receptors required for productive and efficient Adv infections. In addition, because of limitations inherent in Adv infections, such as short-term expression and a non-integrating nature, their application has been precluded from haematopoietic stem cell (HSC) and bone marrow transduction protocols where long-term expression has been required. Therefore, limited research utilising Adv-mediated gene transfer into haematopoietic cells had been conducted. With recent insights into the critical interactions between adenovirus (Adv) and cells, new Adv-mediated gene transduction strategies have now been reported that may overcome these limitations. These new strategies include Adv possessing synthetic polymer coatings, genetically modified capsid proteins or antibody-redirected fibres that can efficiently redirect and retarget Adv to transfer genes into HSC. Additionally, new hybrid Advs, engineered with both modified capsid proteins and novel cis-acting integration sequences, are also being developed which can efficiently deliver and integrate Adv delivered genes into HSC. This is an area of research that is now rapidly gaining momentum in terms of techniques and applications. Here we review the current status of adenovirus-based vectors as a means to achieve high-level gene transfer into haematopoietic cell types.

Genetically modified tumour vaccines (GMTV) in melanoma clinical trials

Since melanoma is a model immunogenic malignancy incurable in the disseminated phase of its natural course different immunotherapeutic approaches are tested in clinical trials. A number of tumour vaccines genetically modified (GMTV), with various immunostimulatory factors, are tested in phase I/II clinical trials. These factors include cytokines, tumour antigens (TA), costimulatory molecules or HLA antigens. We have designed a novel, mixed auto/allogeneic cellular melanoma vaccine modified with the IL-6 and the sIL-6R genes. Preclinical studies in a mouse model demonstrated that the IL-6/sIL-6R based vaccine is able to elicit efficient anti-tumour responses, mediated by CD8+ and NK cells, which resulted in inhibition of the tumour growth, metastases formation and prolonged survival of the animals treated. Irradiation of vaccine cells does not only lead to their sterilisation but also causes increased secretion of exogenous IL-6 and sIL-6R. Since January 1996 we have vaccinated more than one hundred metastatic melanoma patients. Promising clinical results (22% CR+PR, 32% SD) and the evidence of immune responses in the vaccinated patients have prompted us to design a phase III clinical trial which is to be open in 2000.