3006 Background: GW572016 is an oral, reversible and specific receptor tyrosine kinase inhibitor of both ErbB1 (EGFR) and ErbB2 (HER-2/neu). Signaling through these receptors regulates tumor cell proliferation and survival. Results of Phase I trials suggest activity of GW572016 in a number of tumor types including breast cancer. The primary objectives of this study are the assessment of safety and efficacy of monotherapy GW572016 at 1500 mg daily in women with trastuzumab-refractory metastatic breast cancer (MBC). Initially 1250 mg of GW572016 was utilized; the study was amended after 13 patients to administer 1500 mg daily.
METHODS
Eligible patients had ErbB2 overexpressing (IHC) MBC with disease progression following either 1 or 2 prior trastuzumab-containing regimens. Safety (NCI CTC criteria) and efficacy (RECIST criteria) assessments were performed by the attending physician on all patients at 4- and 8-week intervals on treatment.
RESULTS
As of Dec. 2003, 44 patients were enrolled. Preliminary efficacy results regarding the initial 36 patients include 3 partial responses (PR) (8+ weeks, 16+ weeks and 44 weeks) and 5 stable disease (SD) (range 12-36+ weeks). For 15 patients with preliminary safety data, adverse events (AEs) considered by investigators to be study drug related were all grades 1-2 except for one grade 3 rash. For these 15 patients, study drug related AEs that were observed in more than 1 patient were anorexia, nausea, rash, vomiting, diarrhea and weight loss.
CONCLUSIONS
GW572016 1500 mg daily demonstrates preliminary evidence of efficacy in patients with ErbB2-overexpressing MBC refractory to trastuzumab-containing regimens. In the first 36 patients evaluated for efficacy, the clinical benefit rate (PR + SD) is 22%. GW572016 appears well tolerated in this population. Inhibition of both ErbB1 and ErbB2 with GW572016 represents a promising approach in the treatment of breast cancer. [Table: see text].