GlaxoSmithKline this weekend said it would shelve plans to file for approval of its new anticancer agent, lapatinib, with Phase II data at the end of this year, and instead would pursue pivotal studies that would allow it to submit a more complete dossier late 2006, early 2007.

The news follows the unveiling of promising data at the American Society of Clinical Oncology meeting, which revealed a 35% partial response rate amongst breast cancer patients who had not received prior therapy. Specifically, amongst partial respondees,tumour size was reduced by at least 30%. An additional 35% of patients showed stable disease through 12 weeks of therapy.

Lapatinib could have significant potential. In the same drug class as Roche’s big-selling Herceptin (trastuzumab), it is an oral rather than intravenous therapy, which could offer a plethora of benefits in terms of ease of administration and patient compliance. Herceptin, which is currently approved for use in advanced breast cancer, reeled in over 390 million Swiss francs for Roche alone during the first quarter of 2005, up 23% on the previous year [[19/04/05b]].

Lapatinib has been granted fast-track status by the US Food and Drug Administration for the treatment of patients with advanced breast cancer that shows overexpression of the ErbB2 receptor and who have failed previous therapy, including Herceptin.