Pediatric and Neonatal Drug Trials: FDA Requirements Under PREA and Pediatric Study Plans

Studying a new drug in children: what FDA requires before pediatric and neonatal trials

Before a new drug or biologic reaches children, a sponsor has to satisfy two intertwined sets of obligations: a statutory pediatric-study framework (PREA and BPCA, operationalized through the pediatric study plan) and a heightened ethical framework specific to research in minors (21 CFR part 50, subpart D). Layered on top are scientific expectations, drawn from FDA guidance and ICH E11, about extrapolation, formulation, nonclinical support, and the special handling of neonates. This article walks through how each piece works and how it shapes trial design.

The two statutes: one mandatory, one incentive-based

FDA's pediatric-study architecture rests on two laws that operate in opposite directions.

PREA (Pediatric Research Equity Act) is mandatory. A pediatric assessment is required for an application or supplement that introduces a new active ingredient, new indication, new dosage form, new dosing regimen, or new route of administration, unless the requirement is waived, deferred, or inapplicable ⁵²⁵⁴⁵⁵⁵⁸⁶³. The obligation attaches to the specific product change being submitted, and if the sponsor does not comply, FDA can refuse to file the application, issue a complete response letter, or, for deferred studies that come due, issue a noncompliance letter ⁵³. PREA generally does not apply to an orphan-designated indication, although the orphan exemption does not reach products that trigger PREA under section 505B(a)(1)(B) ⁵⁰⁵¹⁵⁷⁵⁸.

BPCA (Best Pharmaceuticals for Children Act) is voluntary and incentive-driven. FDA may issue a Written Request asking a sponsor to conduct studies expected to produce meaningful health benefits in children; the request specifies the study elements needed to qualify ¹⁰⁵¹⁰⁷¹²¹. The statute "does not require the sponsor or application holder to conduct pediatric studies; instead, it creates an exclusivity incentive to encourage such studies" ¹⁰⁵¹⁰⁷¹¹¹¹²¹. Completing the requested studies and submitting reports that fairly respond to the Written Request can earn six months of pediatric exclusivity ¹⁰⁵¹²¹.

The two mechanisms differ in scope. PREA applies only to the indications in the pending application, whereas a BPCA Written Request can be broader, extending to uses of an active moiety that may benefit children even where the drug was never approved in adults ¹¹⁴. FDA does not expect to issue Written Requests solely for studies already required under PREA, though PREA studies described in a Written Request issued before submission can sometimes also qualify for exclusivity ¹¹⁴¹²².

The initial Pediatric Study Plan (iPSP)

The iPSP is where PREA obligations become concrete, and it is required early. FDA expects it to be submitted before the required pediatric assessments, generally no later than 60 calendar days after the end-of-phase 2 (EOP2) meeting, unless FDA and the sponsor agree on another timing ²⁵³³³⁴⁴³. Sponsors are advised not to submit a marketing application or supplement until FDA confirms agreement on the plan ²⁴. When a deferral is requested at NDA/BLA submission, the agreed iPSP is included with the application and fulfills the plan-submission requirement ²⁷.

The iPSP should contain:

An outline of the planned pediatric study or studies, including, to the extent practicable, objectives, design, age groups, endpoints, and statistical approach ²⁴.
Any request for a deferral, partial waiver, or full waiver, with supporting justification ²⁴²⁶²⁸.
A tabular summary of planned nonclinical and clinical pediatric development, categorized by age, flagging studies proposed for deferral and age groups proposed for waiver ²⁶.
A plan grounded in current knowledge of the drug and the disease epidemiology; where more detail is not yet possible, a brief explanation of why ²⁴.

At the scientific level, FDA expects the plan to address the pediatric study type and design, age groups and population, formulations, dose ranges, endpoints, planned modeling and simulation, any pharmacogenomic analyses, and sample-size justification ¹⁵². Age strata should be justified based on how drug response changes with age, maturation of metabolism and excretion, and safety, with studies in all age groups started as early as possible ¹⁷⁷.

Waivers and deferrals

A PREA waiver can be full or partial ³⁰⁴⁸⁵⁹. It may be appropriate where evidence shows the drug would be ineffective or unsafe in all or some pediatric populations (in which case that information goes into labeling) ⁴⁷⁵²⁵⁶, where an indication has extremely limited pediatric applicability because the disease occurs mostly in adults, or where pediatric studies would be impossible or highly impracticable ³⁰²⁶⁵⁹. For an adult-only condition, the iPSP may be very short and simply state that a full waiver will be requested ³⁰⁶¹.

A deferral lets the adult product move forward while pediatric studies continue. Notably, FDA does not formally grant or deny a deferral at iPSP review; it grants the deferral in the approval letter ⁴⁷³⁰. FDA may defer where the drug is ready for adult approval before pediatric studies are complete, where pediatric studies should await additional adult safety or effectiveness data, or for another appropriate reason ⁴⁷²⁶. A deferral request must include a justification, the list of deferred studies, and a completion timeline, with evidence of due diligence and the earliest feasible completion ²⁶⁵³. Material changes to either plan should prompt an amended iPSP as soon as possible ⁴⁷³⁰⁶².

Timing: when pediatric trials can begin

Pediatric exposure is not permitted until there is a sufficient human-safety basis. In the usual case, adult human safety data should be available before pediatric trials begin, and initial pediatric work often starts after adult phase 2 or phase 3 studies have established a reasonable prospect of direct benefit ¹²⁹⁹⁴. In some programs, pediatric studies should not begin until adequate adult safety and efficacy data exist ⁹⁴.

Disease severity shifts this timing. For serious or life-threatening diseases, particularly where the product could be an important advance or therapeutic options are limited, FDA expects relatively early initiation once initial adult safety data and reasonable evidence of potential benefit are available ¹⁸⁷¹⁸²; in some life-threatening programs pediatric studies may begin as early as adult phase 1 or phase 2 ⁹⁴¹⁸⁹. For less serious diseases, later initiation is expected ⁹⁴¹⁶². ICH E11(R1) frames the same principle: pediatric development should not delay completion of adult studies or adult access, serious/life-threatening conditions warrant early pediatric study after initial safety and reasonable evidence of benefit, and other conditions are usually studied later, in phase 2 or 3 or even after substantial adult postmarketing experience ¹⁹⁴¹⁹⁵. Where a disease is predominantly or exclusively pediatric, development proceeds in children, with initial safety usually obtained in adults unless adult study would be uninformative or unsafe ¹⁹⁴.

Ethical safeguards: 21 CFR part 50, subpart D

Research in children carries additional protections beyond ordinary informed consent. Subpart D sets four approval categories, each defined by risk and benefit, and each requiring adequate provisions for the child's assent and the parent(s)' or guardian(s)' permission:

50.51 (minimal risk): the IRB may approve only if the research presents no greater than minimal risk and there are adequate provisions for assent and parental permission ¹⁴⁶.
50.52 (greater than minimal risk, prospect of direct benefit): approvable only if the risk is justified by the anticipated benefit, the benefit-risk relationship is at least as favorable as available alternatives, and assent and permission provisions are adequate ¹⁴²⁹¹.
50.53 (greater than minimal risk, no direct benefit, minor increase over minimal risk): approvable only if the risk is a minor increase over minimal risk, the procedures are reasonably commensurate with the child's actual or expected situation, and the research is likely to yield generalizable knowledge of vital importance about the child's disorder or condition ²⁷⁴. FDA guidance reads "minor increase over minimal risk" narrowly: a slight increase posing no significant threat to overall health, with harms expected to be transient and reversible and the probability of severe pain, discomfort, or harm extremely small or nonexistent ⁵.
50.54 (not otherwise approvable / 407 referral): where a study cannot be approved under 50.51 to 50.53 but presents a reasonable opportunity to understand, prevent, or alleviate a serious problem affecting children's health or welfare, the IRB may refer it for FDA review; the Commissioner then decides, after consultation with an expert panel and public comment, whether it may proceed ¹²²²⁹⁵⁹⁹.

Assent is the child's affirmative agreement, not merely the absence of an objection ¹⁸, and the IRB weighs the child's age, maturity, and psychological state ³⁸. Assent may be waived where the IRB finds and documents that the research is no more than minimal risk, the waiver will not adversely affect the child's rights and welfare, the research could not practicably proceed without it, and additional information will be given where appropriate ³⁸. Assent is not required where the child's capacity is too limited, or where the intervention offers a prospect of direct benefit important to the child's well-being that is available only in the study ³⁸.

Parental permission must be obtained when a child is enrolled, using a form that carries the required elements of informed consent ¹⁴. For 50.51 and 50.52, the IRB may allow one parent's permission; for 50.53 and 50.54, both parents must give permission unless one is deceased, unknown, incompetent, not reasonably available, or lacks legal responsibility ⁴⁶⁸. Permission must be documented consistent with informed-consent requirements ⁴.

ICH E11 reinforces that pediatric development must proceed without compromising the well-being of the participants and that studies and procedures should be designed to be safe, efficient, and ethical, with the pediatric program justified with regulators early and reviewed periodically ¹⁹⁵¹⁹⁶.

Extrapolation: doing the least testing that answers the question

Pediatric extrapolation is the scientific lever that reduces how much must be studied directly in children. FDA treats it as a continuum-based, multidisciplinary assessment of whether disease, pharmacology, and treatment response are "sufficiently similar" between a reference population (adults or older children) and the target pediatric group, focusing on the remaining knowledge gaps and matching study design to the level of uncertainty rather than applying rigid "full/partial/none" labels ¹⁴⁸¹⁵². The resulting plan can range from exposure matching to randomized controlled trials ¹⁴⁸.

Stronger, more complete extrapolation is supported by similar disease course and natural history, common pathophysiology, similar drug metabolism, and similar exposure-response relationships across populations ¹⁵⁹¹⁶²¹⁵⁰. Where disease and response are similar and the PK/PD relationship supports it, matching pediatric exposure to adult exposure can be sufficient ¹⁵³¹⁶⁴¹⁶⁸¹⁶⁹¹⁷¹; for adolescents included in adult trials, adolescent and adult efficacy data may be combined when disease, pharmacology, and response are sufficiently similar ¹⁵⁷. Where similarity is plausible but incomplete, FDA supports partial approaches that bridge the gap with PK studies plus safety data, PK/PD or biomarker data, or targeted pediatric efficacy studies, particularly when blood levels do not reliably track efficacy or the pediatric endpoint differs from the reference population ¹⁵³¹⁶²¹⁴⁹¹⁵⁸¹⁵⁴¹⁵⁵.

Neonates: the hardest population

Neonates are treated as a distinct and unusually demanding population. FDA emphasizes that they are not uniform: studies should span a range of gestational ages, postnatal ages, and body weights unless the drug targets a specific neonatal subpopulation, with subgroup classifications (gestational age, birth weight, postnatal age, and categories such as SGA, LGA, and IUGR) used to make groups more homogeneous ⁶⁶⁶⁷. Postnatal age is a major driver of ADME changes, and extremely preterm infants can differ substantially within the first hours, first days, and beyond the first week of life ⁶⁷.

On dosing and pharmacokinetics, FDA expects sponsors to characterize PK to optimize dose selection ⁶⁸, leveraging adult, older-pediatric, preclinical, and modeling data (population PK, PBPK) to predict neonatal doses ⁶⁶⁶⁷⁷²⁸². Dose selection should account for postmenstrual and postnatal age, and may need adjustment over short intervals as neonates mature; where dose uncertainty is high, titration, adaptive designs, or therapeutic drug monitoring may be needed ⁷³. Population PK is especially valuable because it tolerates sparse, unbalanced data and minimizes blood volume ⁸². Absorption, distribution, protein binding (including bilirubin-displacement risk for highly bound drugs), and developmentally distinct metabolism all require specific attention ⁶⁸⁷⁰. Safety monitoring may need to run longer than in older children, neonates may be uniquely susceptible to drugs crossing the blood-brain barrier, and practical constraints such as limited blood volume favor validated small-volume assays and dried-matrix sampling ⁶⁷⁶⁸⁸⁴⁸⁸. FDA advises planning neonatal studies with a multidisciplinary team that includes neonatologists, NICU nurses, and parents from the outset ⁶⁶.

ICH E11 goes further on the ethics and extrapolation limits: preterm newborns present unique pathophysiology, therapeutic responses, and ethical complexity, and "only rarely" will efficacy extrapolate from adults or older children to preterm infants ¹⁹⁸. Many neonatal diseases are unique or have unique manifestations, often precluding extrapolation and requiring novel outcome measures ²⁰⁰.

Nonclinical support: juvenile animal studies

Where existing nonclinical and human data are insufficient, FDA looks to juvenile animal (developmental) toxicity studies, especially for younger age groups, long-term pediatric exposure, pediatric-first or pediatric-only development, or organs still developing postnatally ¹²⁴¹²⁶¹²⁷¹²⁹¹³³¹³⁵. Timing follows the clinical risk: for long-term pediatric trials, juvenile studies should be completed before initiation ¹²⁷¹²⁹; even for short-term exposure they may need to precede the trial so monitoring can be built in ¹²⁷; and where prior experience is minimal, completed studies are needed before pediatric trials begin ¹²⁷. They are generally not considered important for very short PK studies of one to three doses ¹²⁹¹³³.

Design should be efficient, using the fewest animals necessary and, where feasible, a single study addressing multiple pediatric populations, matched to the developmental stage and windows of concern ¹²⁴¹²⁷¹³⁰¹³⁷. Results feed directly into trial design: identifying pediatric-specific hazards and appropriate monitoring, supplying biomarkers or exposure thresholds for clinical surveillance, informing the age range studied, and, in some cases, indicating that a pediatric trial is not safe to conduct where an unacceptable, unmonitorable adverse effect is likely ¹²⁵¹³⁸¹³²¹⁴².

Formulation and long-term follow-up

FDA expects age-appropriate formulations for each relevant age group, chosen so that dosing is accurate and adherence is enhanced ¹⁰³¹⁰². Practical considerations include whether the dosage form fits the age group (including the size and volume of an adult form), how it will be administered (swallowed, chewed, or mixed with food or liquid), palatability for oral products, any administration device, and excipient toxicity ¹⁰³. FDA advises addressing formulation development early, since an unsuitable adult formulation can otherwise stall a pediatric program ¹⁸²¹⁸⁴.

Finally, because drugs can affect physical and cognitive growth and development, and because those effects may emerge later, ICH E11(R1) advises planning adequate baseline assessments of growth, development, and organ function together with regular follow-up, and notes that long-term studies, postmarketing surveillance, or both may be needed to detect effects on skeletal, behavioral, cognitive, sexual, and immune maturation ¹⁹⁹²⁰⁰. That expectation loops back into study design from the start: the endpoints and follow-up windows a sponsor commits to in the iPSP determine whether developmental safety questions can actually be answered.