Prof. Zlatko Kalvatchev, MD, PhD, DSC

Head of the Center for Viral Diagnosis, University Hospital Nadezhda, Sofia, Bulgaria


Oncolytic viruses (OVs) have demonstrated selective replication and killing of tumor cells. Different types of OVs – adenoviruses, alphaviruses, herpes simplex viruses, Newcastle disease viruses, rhabdoviruses, Coxsackie viruses, vaccinia viruses, etc. – have been applied as either naturally occurring or engineered vectors.

Numerous studies in animal-tumor models have demonstrated substantial tumor regression and prolonged survival rates. Moreover, clinical trials have confirmed good safety profiles and therapeutic efficacy for OVs. Most encouragingly, the first cancer gene-therapy drug – Gendicine, based on oncolytic adenovirus type 5 – was approved by CFDA. Likewise, a second-generation oncolytic herpes simplex virus-based drug for the treatment of melanoma has been registered in the US and Europe as talimogene laherparepvec (T-VEC, Imlygic®).

Various OVs, such as C-REV (Canerpaturev) and CVA21 (CAVATAK), are now actively being developed in phase II as monotherapies, or in combination with immune checkpoint inhibitors against melanoma. Moreover, in glioma, several OVs have clearly demonstrated both safety and a promising efficacy in the phase I clinical trials. Additionally, the safety of several OVs, such as Reolysin®, proved their safety and efficacy in combination with Taxol in breast cancer patients, but the outcomes of OVs as monotherapy against breast cancer have not provided a clear therapeutic strategy for OVs.


Dr. Zlatko Kalvachev graduated in medicine from the Medical Academy in Sofia in 1980. He began working as a military doctor in Rousse. From 1983 to 1986 he was a PhD student in Virology at the Military Medical Academy - Sofia, after which he was appointed as a Fellow. In the year 1994 he started working as a virologist at the Institute for Scientific Research in Caracas, Venezuela. He returned to work at the National Centre of Infectious and Parasitic Diseases in 2011, at the Military Medical Academy (MMA). His professional interests include rickettsia and rapid viral diagnosis, pathogenesis of diseases caused by viruses, rickettsiae, antiviral therapy and more. He is a recognized specialist in virology and microbiology. He has 2 dissertations and has authored more than 150 scientific publications. He is also credited with 4 inventions, 15 innovations and 10 scientific monographs and textbooks. He is a medical doctor, a professor and also the head of the Laboratory of Molecular Virology at MMA. 
Often cited in recent years articles:

  • Kalvatchev Z., Tsekov I., Slavov S., Draganov P. (2010). Effective Light-Upon-Extension (LUX) Real-time PCR Primer Systems for Rapid Detection of Human Viruses. LabMedicine 41, 3: 150-155.
  • Slavov S., Tsekov I. and Kalvatchev Z. (2010). Sequence Variations of the VP1 Gene of Polyomavirus Homins 1 among Bulgarians. Journal of Medical Virology 82, 2: 325-330.
  • TsekovI., Ferdinandov D., HristovaS., Stoyanova, KatsarovK., andKalvachevZ. (2011). Application of real-time PCR technologies for analysis of JCV as a human cancerogen. Biotechnology & Biotechnological Equipment 25, No 1, pp.2262-2265.
  • Tsekov I., Ferdinandov D., Bussarsky V., Hristova S., and Kalvatchev Z. (2011). Prevalence of JC polyomavirus genomic sequences from the large T-antigen and non-coding control regions among Bulgarian patients with primary brain tumors. Journal of Medical Virology 83, 1608-1613.
  • Ferdinandov D., Tsekov I., Bussarsky V. and Kalvatchev Z. (2012). Biotechnologies in the treatment of degenerative disc disease of the cervical spine. Biotechnology & Biotechnological Equipment 26, 4: 3132-3137.
  • Mekouchinov K., Kunchev M., Tsekov I., and Kalvatchev Z. (2012). KI polyomavirus sequenses in respiratory specimens of Bulgarian children. Biotechnology & Biotechnological Equipment 26, 4: 3138-3141.