No abstract

A good understanding and characterization of the dose response relationship of any new compound is an important and ubiquitous problem in many areas of scientific investigation. This is especially true in the context of pharmaceutical drug development, where it is mandatory to launch safe drugs which demonstrate a clinically relevant effect. Selecting a dose too high may result in unacceptable safety problems, while selecting a dose too low may lead to ineffective drugs. Dose finding studies thus play a key role in any drug development program and are often the gate-keeper for large confirmatory studies. In this overview paper we focus on definitive and confirmatory dose finding studies in Phase II or III, reviewing relevant statistical design and analysis methods. In particular, we describe multiple comparison procedures, modeling approaches, and hybrid methods combining the advantages of both. An outlook to adaptive dose finding methods is also given. We use a real data example to illustrate the methods, together with a brief overview of relevant software.

Stroke is a leading global cause of mortality and disability. Less than 5% of patients are able to receive tissue plasminogen activator thrombolysis within the necessary timeframe. Focusing on the process of neuronal apoptosis in the penumbra, which lasts from hours to days after ischaemia, appears to be promising. Here we report that tumour necrosis factor receptor-associated factor 1 (TRAF1) expression is markedly induced in wild-type mice 6 h after stroke onset. Using genetic approaches, we demonstrate that increased neuronal TRAF1 leads to elevated neuronal death and enlarged ischaemic lesions, whereas TRAF1 deficiency is neuroprotective. In addition, TRAF1-mediated neuroapoptosis correlates with the activation of the JNK pro-death pathway and inhibition of the Akt cell survival pathway. Finally, TRAF1 is found to exert pro-apoptotic effects via direct interaction with ASK1. Thus, ASK1 positively and negatively regulates the JNK and Akt signalling pathways, respectively. Targeting the TRAF1/ASK1 pathway may provide feasible therapies for stroke long after onset.

One of the major design considerations for a drug is its pharmacokinetics in the blood. A drug with a short half-life in the blood is less available at a target organ. Such a limitation dictates treatment with either high doses or more frequent doses, both of which may increase the likelihood of undesirable side effects. To address the need for additional methods to improve the blood half-life of drugs and molecular imaging agents, we developed an "add-on" molecule that contains 3 groups: a truncated Evans blue dye molecule that binds to albumin with a low micromolar affinity and provides a prolonged half-life in the blood; a metal chelate that allows radiolabeling for imaging and radiotherapy; and maleimide for easy conjugation to drug molecules. Methods: The truncated Evans blue molecule was conjugated with the chelator NOTA or DOTA, and the resulting conjugate was denoted as NMEB or DMEB, respectively. As a proof of concept, we coupled NMEB and DMEB to c(RGDfK), which is a small cyclic arginine-glycine-aspartic acid (RGD) peptide, for targeting integrin a v b 3 . NMEB and DMEB were radiolabeled with 64 Cu and 90 Y, respectively, and tested in xenograft models. Results: The resulting radiolabeled conjugates showed a prolonged circulation half-life and enhanced tumor accumulation in integrin a v b 3 -expressing tumors. Tumor uptake was markedly improved over that with NOTA-or DOTA-conjugated c(RGDfK). Tumor radiotherapy experiments in mice with 90 Y-DMEB-RGD showed promising results; existing tumors were eliminated. Conclusion: Conjugation of our novel add-on molecule, NMEB or DMEB, to potential tracers or therapeutic agents improved blood half-life and tumor uptake and could transform such agents into theranostic entities. Thegoalofdr ug development is to achieve high activity and specificity for a desired biologic target. However, many potential pharmaceuticals that meet these criteria fail as therapeutics because of unfavorable pharmacokinetics, in particular, rapid blood clearance, which prevents the achievement of therapeutic concentrations. For some drugs, the administration of large or frequently repeated doses is required to achieve and maintain therapeutic levels (1) but can, in turn, increase the probability of undesired side effects. One chemical modification that delays the rate of drug clearance and has been effective for some drugs is the addition of polyethylene glycol (PEG) (2). However, recent studies showed that PEGylation of drugs has disadvantages, including immunogenicity caused by the development of anti-PEG antibodies, heterogeneity of the PEGylated drugs, and decreased biologic activity and bioavailability of the drugs (1,3).To address the need for additional methods to improve the blood half-life of drugs and molecular imaging agents, we made use of molecules with a high affinity for albumin. We previously developed a radiolabeled truncated derivative of Evans blue (EB) that allowed imaging of the blood volume because of the affinity of EB for albumin (4). This result encouraged us to e...