Precision Dosing of Alemtuzumab

The hypothesis is that the model-informed dosing regimen will prospectively allow the precision dosing of alemtuzumab to target Day 0 levels to fall between 0.15-0.6ug/mL in greater than 80% of patients. The investigators have chosen a conservative pilot study approach, and the aim is to achieve Day 0 alemtuzumab levels between 0.15-0.6ug/mL in greater than 60% of 20 patients enrolled in this pilot study based on a Simon two-stage design as detailed below. A Simon two-stage design (Simon, 1989) is being used. The null hypothesis that 30% of patients will achieve a Day 0 alemtuzumab level between 0.15-0.6ug/mL will be tested against a one-sided alternative that the alemtuzumab dose modification will result in 60% of patients achieving a Day 0 alemtuzumab level between 0.15-0.6ug/mL. In the first stage, 7 patients will be accrued. If there are 2 or fewer patients that achieve Day 0 alemtuzumab levels within the range of 0.15-0.6ug/mL, the study will be stopped. Otherwise, 13 additional patients will be accrued for a total of 20. The null hypothesis will be rejected if 11 or more patients achieve a Day 0 level of 0.15-0.6ug/mL within the total 20 patients. This design yields a type I error rate of 0.04 and power of 0.82 when the true response rate is 0.60. The investigators will enroll up to 30 patients in order allow for subject withdrawal, but will stop enrollment once 20 patients reach Day 0.