Btk Inhibitors - Pointing the Way to the Future of Targeted Therapies?

07 May 2012 Gustav Ando

Tolero Pharma is the third drug firm in a matter of months to make a decisive investment in the Bruton's tyrosine kinase (Btk) research area, following its USD130 million deal with MannKind to develop and commercialise its programme in this area. The announcement follows hot on the heels of Celgene's acquisition of Avila Therapeutics back in January, which centred around the Btk inhibitor AVL-292, and the month before that saw Johnson & Johnson acquire another Btk inhibitor, PCI-32756, from Pharmacyclics. The Celgene and Johnson & Johnson deals were worth fractionally below USD1 billion each, and provided some big validation of the commercial potential of this target.

Unravelling Tolero's Deal
Tolero's deal is a slightly different beast - for a start, it is dealing with research that has not gone into completed Phase I trials. But interestingly, it also contains an unusual provision that MannKind maintains an option to re-acquire - yes re-acquire - the rights to the programme at pre-specified terms until 60 days after the conclusion of the first Phase I study. As such, it provides a degree of uncertainty to Tolero's role in the development programme, but it also may signify that much deeper integration may eventually occur between the two companies.

Promising Signs for Btk inhibitors
So why the sudden interest in Btk? In clinical trials to date, the Btk inhibitors have shown a wide range of efficacy, particularly in blood cancers such as lymphoma, multiple myeloma and leukaemia, with potential in other diseases such as rheumatoid arthritis. Interestingly, toxicity doesn't seem to be too bad either - in a Phase I/II trial of PCI-32765, the drug showed 90% response rate in advanced chronic lymphocytic leukaemia (CLL) patients, and side-effects were comparatively uncommon. The data caused a fair amount of commotion at the annual meeting of the ASH at the tail-end of last year.

The technology is about to hit Phase III in 2012, and we'll only likely begin to gain a full insight into its potential in diseases with high unmet clinical need in 2013. In the meantime, it wouldn't be surprising to see more of the larger drugs firms scrambling to acquire clinical assets in this area.


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