Oncolytic herpes virus

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Oncolytic herpes virus
Herpes simplex virus TEM B82-0474 lores.jpg
TEM micrograph of a herpes simplex virus.
Virus classification
Group:
Group I (dsDNA)
Order:
Herpesvirales
Family:
Herpesviridae
Subfamily:
Alphaherpesvirinae
Genus:
Simplexvirus
Species:
Herpes simplex virus 1
Variety:
Oncolytic herpes virus

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Many variants of herpes simplex virus have been considered for viral therapy of cancer; the early development of these was thoroughly reviewed in the journal Cancer Gene Therapy in 2002.[1] This page describes (in the order of development) the most notable variants—those tested in clinical trials: G207, HSV1716, NV1020 and Talimogene laherparepvec (previously Oncovex-GMCSF).

File:Herpes virus00.jpg
Electron Micrograph of herpes virus

HSV1716

HSV1716 is a first generation oncolytic virus developed by The Institute of Virology, Glasgow, UK, and subsequently by Virttu Biologics (formerly Crusade Laboratories, a spin-out from The Institute of Virology), to selectively destroy cancer cells. The virus has the trade name SEPREHVIR. It is based on the herpes simplex virus (HSV-1). The HSV1716 strain has a deletion of the gene ICP34.5. ICP34.5 is a neurovirulence gene (enabling the virus to replicate in neurons of the brain and spinal cord). Deletion of this gene provides the property of tumor-selective replication to the virus (i.e. largely prevents replication in normal cells, while still allowing replication in tumor cells), although it also reduces replication in tumor cells as compared to wild type HSV.[2][3]

A vital part of the normal mechanism of HSV-1, the ICP34.5 protein has been proposed to condition post-mitotic cells for viral replication. With no ICP34.5 gene, the HSV-1716 variant is unable to overcome normal defences of healthy differentiated cells (mediated by PKR) to replicate efficiently. However, tumour cells have much weaker PKR-linked defences, which may be the reason why HSV1716 effectively kills a wide range of tumour cell lines in tissue culture.

An HSV1716 variant, HSV1716NTR is an oncolytic virus generated by inserting the enzyme NTR into the virus HSV1716 as a GDEPT strategy.[4] In-vivo, administration of the prodrug CB1954 to athymic mice bearing either A431 or A2780 tumour xenografts, 48 hours after intra-tumoral injection of HSV1790, resulted in a marked reduction in tumour volumes and significantly improved survival compared to administration of virus alone. A similar approach has been taken with a variants of HSV1716 that expresses the noradrenaline transporter to deliver radioactive iodine into individual infected cancer cells, by tagging a protein that cancer cells transport. The nor-adrenaline transporter specifically transports a compound containing radioactive iodine across the cell membrane, using genes from the virus. The only cells in the body that receive a significant radiation dose are those infected and their immediate neighbours.[5]

Clinical trials

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G207

G207 was constructed as a second-generation vector from HSV-1 laboratory strain F, with ICP34.5 deleted and the ICP6 gene inactivated by insertion of the E. coli LacZ gene.[12]

Two phase I clinical trials in glioma were completed.[13][14][15] The results of the first trial were published simultaneously with the first trial of HSV1716 in 2000, with commentators praising the demonstration of safety of these viruses when injected into brain tumours but also expressing disappointment that viral replication could not be demonstrated due to the difficulty of taking biopsies from brain tumours.[16]

NV1020

NV1020 is an oncolytic herpes virus initially developed by Medigene Inc. and licensed for development by Catherex Inc. in 2010.[17] NV1020 has a deletion of just one copy of the ICP34.5 gene and ICP6 is intact.[18] A direct comparison of NV1020 and G207 in a mouse model of peritoneal cancer showed that NV1020 is more effective at lower doses.[19]

Clinical trials

A Phase I/II study completed in 2008 evaluating NV1020 for treatment of metastatic colorectal cancer in the liver.[20] The study assessed tumour response by CT scan and FDG-PET scans, showing 67% of patients had an initial increase in tumour size then followed by a decrease in 64% of patients.[21][19]

Talimogene laherparepvec

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Main article: Talimogene laherparepvec

Talimogene laherparepvec is the USAN name for the oncolytic virus also known as 'OncoVEX GM-CSF'. It was developed by BioVex Inc. (Woburn, MA, USA & Oxford, UK) until BioVex was purchased by Amgen in January 2011.[22]

It is a second-generation herpes simplex virus based on the JS1 strain and expressing the immune stimulatory factor GM-CSF.[23][24] Like other oncolytic versions of HSV it has a deletion of the gene encoding ICP34.5, which provides tumor selectivity.[25] It also has a deletion of the gene encoding ICP47, a protein that inhibits antigen presentation,[26] and an insertion of a gene encoding GM-CSF, an immune stimulatory cytokine.[2][3] Deletion of the gene encoding ICP47 also puts the US11 gene (a late gene) under control of the immediate early ICP47 promoter. The earlier and greater expression of US11 (also involved in overcoming PKR-mediated responses) largely overcomes the reduction in replication in tumor cells of ICP34.5-deleted HSV as compared to wild type virus, but without reducing tumor selectivity.

Clinical trials

Including phase III : See Talimogene laherparepvec

See also

References

  1. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Clinical trial number NCT01721018 for "Intrapleural Administration of HSV1716 to Treat Patients With Malignant Pleural Mesothelioma" at ClinicalTrials.gov
  11. ↑ Clinical trial number NCT00931931 for "HSV1716 in Patients With Non-Central Nervous System (Non-CNS) Solid Tumors" at ClinicalTrials.gov
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Clinical trial number NCT00028158 for "Safety and Effectiveness Study of G207, a Tumor-Killing Virus, in Patients With Recurrent Brain Cancer" at ClinicalTrials.gov
  15. ↑ Clinical trial number NCT00157703 for "G207 Followed by Radiation Therapy in Malignant Glioma" at ClinicalTrials.gov
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ 19.0 19.1 Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ Clinical trial number NCT00149396 for "Safety and Efficacy of a Genetically Engineered Herpes Simplex Virus NV1020 to Treat Colorectal Cancer Metastatic to Liver" at ClinicalTrials.gov
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  24. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  25. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  26. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

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