Once agreement has been reached on the necessity of including children in trials of new tuberculosis treatment regimens, the specific barriers to the involvement of children must be identified and then overcome (Table 1). The difficulty of culture confirmation of active tuberculosis among children is well known [17]. Because a positive culture is both an enrollment criterion and the primary endpoint of phase II and III clinical trials for tuberculosis treatment, some observers have concluded that tuberculosis treatment trials cannot be done among children. This limitation is quite real—because of it, pediatric trials are not the setting for the definitive evaluation of the efficacy of a new drug or treatment regimen. However, it does not mean that treatment trials cannot be done among children.

Improved specimen collection techniques (e.g., induced sputum and string test) can provide culture confirmation in a higher percentage of pediatric patients than previously thought possible [23–26]. Furthermore, case definitions for culture-negative pediatric tuberculosis can be used in clinical trials, as criteria both for enrollment and for evaluating efficacy [27,28]. While imperfect, these case definitions can be applied by an events committee blinded to treatment assignment to ensure unbiased assessment of diagnosis and response to treatment.

Although concerns about pediatric-specific side effects have led some to argue against inclusion of children in clinical trials, these concerns fail to recognize that new drugs will be used off-label among children, in the absence of data on pediatric pharmacokinetics and tolerability, as soon as they are approved for adults. Children are indeed vulnerable participants in research because of their inability to provide fully informed consent. However, an overzealous attempt to protect some children from the possible harms of research perversely causes harm, by either denying access to treatment or through exposing children to the risks of inappropriate dosages of new medications.

Effective therapy is available for drug-susceptible tuberculosis. However, the limitations of current first-line tuberculosis treatment should be recognized. Despite the appeal of our current nomenclature of “short-course therapy,” a six-month treatment duration leads to worrisome numbers of patients who do not complete treatment in many programmatic situations [29–32]. The side effects of current regimens are appreciable as well: high rates of bothersome side effects, such as nausea and vomiting, and substantial rates of serious adverse events, such as hepatotoxicity [33]. In spite of the availability of effective therapy for drug-susceptible tuberculosis, new agents should still be evaluated among children; there is much room for improvement in “short-course therapy.”

At what points in tuberculosis drug development should studies be undertaken in children? This crucial question requires discussion among investigators, the pharmaceutical industry, advocates, and regulatory officials. As a starting point for such discussions, we offer initial suggestions in Table 2. If children are to be involved at specific points in drug development, appropriate timelines are needed for initial work on formulations and pharmacokinetic studies among children. It is inappropriate to wait until the drug development plan for a new drug or regimen has been completed in adults before beginning its evaluation in children.

What kinds of trials should be undertaken among children? Not all phase III trials in adults need repeating in children; it is highly likely that children will respond well to a new regimen if given a drug formulation and dose that achieves pharmacokinetic parameters comparable to those among adults. Questions that are specific to children, or where answers from adults are unlikely to extrapolate to children, require separate evaluation. Key examples of studies that must be done among children are those assessing the pharmacokinetics and tolerability of new drugs [17].

It can be difficult to obtain blood specimens by venipuncture from very young and very ill children. This challenge should not preclude pharmacokinetic studies of new antituberculosis drugs among children; more efficient study designs and techniques for use of ultra-small quantities of blood can overcome this limitation. Sparse sampling schemes analyzed with Bayesian statistical methods that incorporate pharmacokinetic data from adults, in addition to knowledge about maturation of metabolic pathways in children, facilitate the design and implementation of pharmacokinetic studies in children [34].

An instructive example of optimizing methodologies for pharmacokinetic studies for children comes from malaria research. Severe malaria is predominantly a disease of young children, so it is critical that the pharmacokinetics of antimalarial drugs among infants and young children be well understood. In these studies, very small samples of blood (100 microliters) obtained by finger- or heel-stick are blotted onto filter paper, allowed to dry, stored at room temperature, and later used to determine concentrations of antimalarial drugs [34,35]. Thus, pharmacokinetic studies can be extended to infants and young children, and such samples can be obtained under field conditions where the disease is common. The extension of these techniques to the study of new antituberculosis drugs requires further research, but the challenge of pharmacokinetic sampling among young children calls for this kind of innovation.

There are many regulatory steps between the development of a study protocol and its implementation at study sites. Some have expressed concern that involving children in drug development will slow down the already lengthy timeline for study implementation by triggering more rigorous regulatory review. This concern may be well founded. However, key funding and regulatory agencies have policies and incentives to encourage evaluation of new drugs among children for conditions, like tuberculosis, that are common among that age group (the US National Institutes of Health requires specific justification if children are not included in a study). Some of those incentives, such as extended patent protection for the United States market, are unlikely to encourage tuberculosis drug development efforts for children. However, the US Food and Drug Administration has recently been authorized to take additional steps to promote the inclusion of children in drug development [36], and the European Union now requires that any new drug that could potentially be used in children have a Pediatric Implementation Plan for the drug to be licensed in adults [37]. Other groups are developing alternative incentive structures for diseases of poverty, such as tuberculosis [38].