There were three open-label, phase I clinical trials in
patients with refractory (grade 4) HER2-positive metastatic
breast cancer (Table 1), which were primarily
designed to determine the safety, maximum tolerated
dose and pharmacokinetics of trastuzumab [49]. The
weekly schedule of i.v. infusion was based on the expected
clearance of trastuzumab calculated from preclinical
studies and was continued until disease progressed. The
dose of cisplatin used was 50 or 100 mg/m2. As is usual
in such studies, relatively low numbers of patients were
recruited in these phase I clinical trials (n - 15-17) and
the enrollment was completed in short period of time.
Trastuzumab was well tolerated at all doses from 10-
500 mg i.v. and a maximum tolerated dose was not
reached. In the single-agent trials, serious adverse events
were recorded in four patients, but none were considered
related to the administration of trastuzumab. Trastuzumab
was also well tolerated in combination with cisplatin
and the frequency and nature of adverse events
was similar to that previously described during clinical
experience with cisplatin alone. With respect to pharmacokinetics,
the serum half-life of trastuzumab increased
with increasing dose, ranging from about one day with