Bayesian continual reassessment method for dose-finding trials infusing T cells with limited sample size

On the feasibility of pediatric dose-finding trials in small samples with information from a preceding trial in adults

We consider the case of pediatric dose-finding trials with extremely limited sample size. The operating characteristics of the standard design, the Continual Reassessment Method (CRM), are only well described for sample sizes of about 20 patients or more. In this simulation study, we assume the situation of a pediatric trial with only 10 patients and a preceding dose-finding trial in adults. Based on the adult data, we reduce the set of pediatric doses and formulate (partially) informative prior distributions for the pediatric trial. Our simulations show that such small pediatric dose-finding trials with robustified priors may provide sufficient operating characteristics.

Overall success rate of a safe and efficacious drug: Results using six phase 1 designs, each followed by standard phase 2 and 3 designs

To evaluate the overall success rate of a new drug, phase 1, 2, and 3 trials were simulated using eight toxicity and two non-decreasing efficacy profiles. Six phase 1 designs including the standard 3 + 3, CCD, BOIN, mTPI, mTPI-2, and CRM were considered with standard phase 2 and 3 designs.

Based on our results, phase 1 design recommendations are provided when data informing the general shape of the dose-toxicity curve exist. If a large jump in toxicity between dose levels is expected, the standard 3 + 3 design is recommended; it more often recognized when the MTD was exceeded and had the highest overall success rates. If gradually increasing toxicity is expected, a nonstandard design other than the CRM is recommended. Nonstandard designs were more aggressive in dosing and MTD estimation than the standard 3 + 3 and had higher overall success rates, but the CRM was too aggressive and most frequently overestimated the true MTD. If fairly constant, safe toxicity is expected across dose levels, the BOIN or CRM designs are recommended; they escalated to the highest dose most frequently with superior overall success rates.

Without data informing the shape of the dose-toxicity curve, nonstandard phase 1 designs with a modified excessive toxicity rule more easily eliminating unsafe dose levels are recommended. With this modification, MTD overestimation error decreased and overall success rates were similar or higher with nonstandard designs. Among nonstandard designs, the modified CCD and BOIN perform well and are as transparent and simple to implement as the standard 3 + 3 design.

Developing a Bayesian adaptive design for a phase I clinical trial: a case study for a novel HIV treatment

The design of phase I studies is often challenging, because of limited evidence to inform study protocols. Adaptive designs are now well established in cancer but much less so in other clinical areas. A phase I study to assess the safety, pharmacokinetic profile and antiretroviral efficacy of C34-PEG₄ -Chol, a novel peptide fusion inhibitor for the treatment of HIV infection, has been set up with Medical Research Council funding. During the study workup, Bayesian adaptive designs based on the continual reassessment method were compared with a more standard rule-based design, with the aim of choosing a design that would maximise the scientific information gained from the study. The process of specifying and evaluating the design options was time consuming and required the active involvement of all members of the trial's protocol development team. However, the effort was worthwhile as the originally proposed rule-based design has been replaced by a more efficient Bayesian adaptive design. While the outcome to be modelled, design details and evaluation criteria are trial specific, the principles behind their selection are general. This case study illustrates the steps required to establish a design in a novel context. Copyright © 2016 John Wiley & Sons, Ltd.