GlaxoSmithKline (GSK) has discontinued its research on an antibiotic co-developed by Anacor Pharmaceuticals after some patients were found to have built resistance to the drug.
All rights for the compound, known as GSK2251052, will now be returned to Anacor and the move followed the February suspension of several early- to mid-stage trials involving the drug.
Since then GSK has been analysing a "microbiological finding" in a small subset of patients who had been taking the antibiotic in a phase IIb trial investigating its use in the treatment of complicated urinary tract infections (cUTI).
At the time, Anacor was hopeful GSK would resume the trials when its investigation had been concluded, but it now appears this investigation, which included additional pre-clinical research, uncovered resistance in some patients participating in the cUTI trial which would have a serious bearing on the efficacy of the treatment.
Anacor licensed GSK2251052 to GSK in July 2010 as part of an existing R&D collaboration and hopes had been high for the antibiotic's potential to target Gram-negative bacteria, for which few treatments exist, and those that are available tend to be poorly-tolerated.
Resistance to existing therapies also continues to be a growing problem for patients with Gram-negative infection, increasing the need for new treatments.
GSK is still involved in research in this area, however, and in September, 2011, the company was awarded $38.5m from the Biomedical Advanced Research and Development Authority (BARDA) to support its efforts.
Sanofi is also researching antibiotics for the treatment of Gram-negative infections, signing an agreement with Rib-X Pharmaceuticals in July, 2011.
Despite the discontinuation of the GSK2251052 collaboration, GSK is still working with Anacor through the funding of its research activities in tuberculosis.