PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas) No concurrent chemotherapy Endocrine therapy: At least 2 weeks since change in dosing and type of immunosuppressive drugs unless due to progression of disease Radiotherapy: At least 4 weeks since prior radiotherapy No concurrent radiotherapy Surgery: At least 4 weeks since prior major surgery (except diagnostic surgery) Other: At least 30 days or 5 half-lives since other prior investigational drugs or whichever is longer