Nervous system disease: A new outlet for an old drug?

The disease goes by the lengthy moniker of human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis or 'HAM/TSP' for short. It's developed by a subset of people infected with the sexually-transmitted retrovirus HTLV-1, which infects up to 20 million people worldwide, mainly in equatorial regions. The result is a chronic, progressive demyelinating disease of the lower extremities, leading to muscle weakness, spasms, paraplegia and urinary problems.

Twenty-four HAM/TSP patients, who had had the disease for up to 50 years, took the drug -- prosultiamine -- daily as part of the open-label study. Twelve weeks later, most of the patients were more mobile -- they walked more quickly and were faster at going down stairs. Bladder capacity increased and bladder problems lessened, Tatsufumi Nakamura and colleagues report.

The condition is currently managed with drugs that alter the immune response, such as corticosteroids and interferon-alpha. But their efficacy is contested, and they manage symptoms rather than cure the disease. Prosultiamine, on the other hand, reduced levels of the HTLV-1 provirus in the patients' blood, a sign that the drug may be altering the underlying pathology rather than just managing symptoms.

Results from an earlier trial suggested the drug may prove useful therapeutically, but treatment lasted just 2 weeks. Here, the drug produced favourable results with no serious adverse side effects after 3 months of treatment.

Prosultiamine is already used in the clinic to treat a couple of brain disorders induced by vitamin B1 deficiency. Studies have shown it to be safe and stable. The data presented here suggest that prosultiamine could be a promising therapeutic tool for HAM/TSP, so the next step is larger, randomised, blinded clinical trials to assess its therapeutic value.

A commentary by Jun-Ichi Kira will be published at the same time in BMC Medicine.