25 March 2013

Virus against melanoma: the results are moderately positive

The active component of the talimogene laherparepvec drug developed by Amgen is an oncolytic virus. Such viruses selectively penetrate into malignant cells, where they behave like ordinary viruses. Using the resources of the cell, they multiply until the cell overflows with viral particles and dies, releasing them into the extracellular space, from where the "infection" spreads to neighboring tumor cells.

The attractiveness of drugs based on such viruses lies in the selectivity of their action and, accordingly, the absence of undesirable effects on healthy tissues. For the first time, experts became interested in oncolytic viruses about two decades ago. However, what looked very promising in the laboratory turned out to be very difficult to transfer into clinical practice. One of the problems is that oncolytic viruses are effective only if they penetrate deep into the tumor.

The developers of talimogen took as the basis of the drug a genetically modified herpes simplex virus that selectively infects tumor cells. An additional genetic modification, consisting in the insertion of the granulocyte-macrophage colony stimulating factor (GM-CSF) gene, endowed the virus with the ability to attract immune system cells to the area of the tumor infected by it.

More than 400 non-operated patients with melanoma of stages IIIB, IIIC or IV participated in a global randomized open clinical trial of phase III, the purpose of which is to evaluate the safety and efficacy of a new drug compared to control therapy consisting in the introduction of granulocyte-macrophage colony stimulating factor. Participants were randomly divided into an experimental group and a control group in a ratio of 2:1. Patients of the experimental group are injected with talimogen laherparepvec directly into the tumor focus every two weeks, while patients of the control group are given intradermal injections of granulocyte-macrophage colony stimulating factor during the first 14 days of each 28-day cycle.

According to the preliminary results published by the company, experimental therapy provided a 6-month reduction in the size of tumor foci in 16% of patients. For patients in the control group, this figure was only 2%. Currently, the clinical trial is ongoing, and the maximum duration of treatment planned within it is 18 months.

According to the company's statement published in the press, a statistically significant difference for the values of "a stable proportion of patients responding to therapy, defined as the level of full or partial response to treatment that persists for at least six months," means that the primary objective of the clinical trial has already been achieved.

During this year, the company's specialists hope to obtain results concerning the ability of the drug to improve the overall survival of patients, the assessment of which is the second most important task of the study.

Specialists in the treatment of melanoma, who are not related to the study, note that 16% is a fairly low figure. In addition, the effectiveness of the experimental drug is compared with the effectiveness of the approach not used for the treatment of melanoma in routine clinical practice.

At the same time, the relatively low effectiveness of experimental therapy may be due to the fact that only in one third of patients with advanced stages of melanoma, the tumor affects the skin and, accordingly, is available for administration of the drug. In most patients with this diagnosis, melanoma has already spread to inaccessible organs such as the brain or liver.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru according to Medical News Today:
Virus-Based Melanoma Drug Shows Promise In Trial.


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