Novel Derivatives of Valproic Acid and Acyclovir as Selective Anti-Cancer Agents

Technology
Histone deacetylase inhibitors (HDACis) have emerged as a powerful new class of anticancer agents acting through the regulation of histone and other proteins acetylation. However, the current FDAapproved HDACis SAHA and FK228 used for treatment of CTLC patients have serious limitations hindering their use, including ineffectively low concentrations in solid tumors and cardiac toxicity. A novel compound derived from the known histone deacetylase inhibitory (HDACi) molecule, valproic acid, was developed by us (AN446). Valproic acid is a widely used drug for treatment of neurological disorders, which has recently gained interest as an anticancer agent. Giving its HDAC inhibitory activity, many clinical studies for cancer therapy with valproic acid were initiated (http://clinicaltrials.gov).
Below, we describe novel the properties of the lead valproic acid derivative: valproyl ester-valpromide of acyclovir (AN446) possessing potent in vitro and in vivo anticancer activity.

The Need and Potential Application
Cancer has become one of the major focus areas for pharmaceutical and biotechnology companies because of the high unmet need for improved treatments for multiple types of cancer.
New approaches to combat the significant morbidity and mortality caused by cancerous diseases are urgently needed. Target cancers include glioblastoma, breast, lung and colon carcinomas, HPV (cervical carcinoma), Kaposi's sarcoma virus, lymphoproliferative and bladder carcinoma in transplant patients.

Advantages of the Derivatives

• Straight forward and cost effective synthesis
• Orally bioavailable
• Unique mechanism of action which includes HDAC inhibition as well as inhibition of DNA synthesis
• Increase the potency of valproic acid as histone deacetylase inhibitor and as anticancer agent
• Overcome resistance to chemotherapy (e.g., Paclitaxel and doxorubicin)
• Compounds are well tolerated (in initial toxicology studies)

Stage of Development
The lead molecule AN446, in vitro and in vivo, was shown to be a selective inducer of cancer cell mortality, acting by:

• Reducing HDAC expression and activity resulting in histone (and other proteins) acetylation and reduced methylation
• Decreased expression of TK1 and TK2, pro-angiogenic and DNA repair proteins, c-Myc in cancer cells
• Increasing ROS in cancer cells but reduction of insult-induced ROS in normal cells
• Inducing DNA breaks and reducing DNA damage response, thereby leading to apoptosis
• Inducing collapse of the mitochondrial membrane potential
• Inhibiting proteasome activity
• Exposure of the EBV(+) Gastric carcinoma and Burkitte's lymphoma cells positive for EBV to AN446, significantly increased the expression of viral lytic genes vTK, VPK, BZLF1 (early genes) and the glycoprotein 350 (late gene) normally expressed only during the lytic-replication stage of the virus life cycle, while decreasing EBNA1, the latent gene. It is of note, that whereas AN446 increased the lytic viral thymidine kinase (vTK), it repressed the transcription of the cellular TK1. The dormant virus in the tumor can be used as a "Trojan-horse" to assist in specifically killing the cells that harbor them, and AN446, by reactivating the viral genes, is a candidate drug for this purpose.

AN446 was tested in vivo in various animal models including syngeneic 4T1, Lewis lung carcinoma mouse models and U251 glioblastoma xenograft. The results demonstrated cancer-specific activity, as apoptosis was induced differentially in the tumors and not in other organs following oral administration of the compound.
AN446 augmented the anticancer activity of doxorubicin and paclitaxel by potentiating its apoptotic activity of the tumor cells. In combination with doxorubicin, AN446 reduces cardiotoxicity and damage to the kidney by diminishing doxorubicin-induced ROS and apoptosis of normal cells.

Patents
Worldwide patent application (PCT/IL2008/000443)

Project manager

Adi Elkeles
BD Manager

Project researchers

Ada Rephaeli
T.A.U Tel Aviv University, Medicine-Sackler Faculty
Felsenstein Medical Res Center-Beilinson

Abraham Nudelman
Bar-Ilan University (BIU),