"The BCG" is a vaccine against tuberculosis (TB) that many in the UK will remember receiving in their school days, not least because it often leaves a characteristic scar at the administration site. Since 2005 however, the BCG vaccine has been phased out of schools in the UK and is typically only offered to individuals deemed at higher risk of contracting TB.

In addition to its use in the treatment of TB, BCG has been trialled as an immunotherapeutic for the treatment of cancers. Notably in the treatment of early-stage bladder cancer, intravesically administered BCG has been highly successful.

In the wake of the ongoing Covid-19 pandemic, attention has once again turned to the BCG vaccine with reports suggesting that BCG may have a protective effect against the virus. Investigations are ongoing with a number of questions still to be answered (described in more detail in the linked article below).

Regardless of whether BCG will actually evolve into a Covid-19 therapeutic, the recently emerging reports are a reminder that beyond the famous examples of thalidomide and aspirin (among others), there is undoubtedly a wealth of molecular mechanisms still to be uncovered that may lead to therapeutically repurposed drugs.

In Europe, though methods of treatment performed on the human body are not patent-eligible, products for use in such methods are not exempt.

New medical uses of known substances are certainly patentable, and with the high costs associated with developing a therapeutic from scratch, it could pay to teach an old dog new tricks.