- From the projected start of scheduled study treatment, the following time periods must have elapsed: 4 weeks or 5 half-lives (whichever is shorter)from any investigational agent, 4 weeks from cytotoxic therapy (except 23 days for temozolomide and 6 weeks from nitrosoureas), 6 weeks from antibodies, or 4 weeks or 5 half-lives (whichever is shorter) from other anti-tumor therapies.