After causing childhood chickenpox, VZV (varicella zoster virus) remains latent in nerve tissues, held in check by the immune system. It remains there until the immune system is compromised, perhaps as a consequence of stress, illness or just old age. At such times, the virus may reactivate causing shingles particularly in the elderly and presenting as a painful strip of vesicles, usually around the trunk, with the risk of severe, chronic pain and persistent after-effects.

Shingles stings and itches on and under the skin, and at times, the pain is intense. After a few days, a rash becomes apparent as a band or collection of small vesicles on the body, which in the most severe cases, appear on the face, affecting the trigeminal nerve, which ends under the eye. Because of the risk of complications such as compromised sight or hearing, people suffering from shingles on the face should seek medical help quickly, and other sufferers should do so to reduce the risk of chronic pain. 50% of all shingles patients are affected by chronic pain of varying severity.

The irritating vesicular eruptions develop into small water-filled vesicles, and at their peak, out-breaks can vary from mild irritation to extreme, in-tense pain. Eventually, the vesicles heal leaving small scabs, and some five weeks after the first symptoms, all the pain from the vesicles disappears, with the skin free from blemishes. However, many sufferers experience protracted pain, lasting up to several years.

Post-herpetic Neuralgia
VZV causes childhood chickenpox, and then remains latent in the nervous tissue. It may reactivate in later life, resulting in shingles with the ensuing chronic pain, called PHN (post-herpetic neuralgia). The nervous system is involved in shingles, with more serious and complex symptoms than chickenpox. The pain is a consequence of the virus causing nerve tissue damage, generating additional nerve impulses, and thereby, pain. The damage causes chronic pain that is extremely hard to treat, although regular pain-killers do help. The pain is often disabling and can result in disturbed sleep, weight-loss and depression.

A Shortage of Drugs
VZV causes shingles outbreaks on 3.5 million sufferers in the West each year, with as many as 95% of the world’s adult population carrying VZV.  The risk of contracting shingles increases with age.

Current antiviral pharmaceuticals include acyclovir and valaciclovir, which exert an effect on the vesicles that erupt, but only a marginal effect on chronic pain. A broad selection of analgesic drugs and pain killers are used against the chronic pain, with varying results.

MIV-606
Medivir’s theory is that a substance exerting a good effect on shingles would have to be far more potent than current drugs and would have to quickly reach the nerve cells that VZV damages, thereby causing PHN.
MIV-606 is 100-400 times more powerful than existing pharmaceuticals and can also reach the nerve tissue. The drug would have to be administered as soon as the symptoms become apparent but with greater awareness of how shingles symptoms are expressed, the better the chances of successful medication.

Heading for Phase III
MIV-606 has passed through clinical phase II with positive results. Discussions with forthcoming partners are in a conclusive phase regarding outlicensing ahead of the phase III program, which is the next step for MIV-606.The objective of these phase III trials is to verify MIV-606’s effect on chronic pain. At present, there is no drug registered for this indication.

MIV-606 is also active on other herpes viruses such as HSV, which causes cold sores and genital sores, and the Epstein-Barr virus, which causes mono-nucleosis, more commonly known as glandular fever. Moreover,it is active against HHV-6 (herpes virus type 6) which may be involved in MS.