How First-Time-in-Human Studies Are Being Performed: A Survey of Phase I Dose-Escalation Trials in Healthy Volunteers Published Between 1995 and 2004

A review of dose escalation for FDA-approved products treating solid tumors and hematological malignancies in first-in-human trials

First-in-human (FIH) dose-escalation trials on oncology should prioritize safety and emphasize efficacy. We reviewed the FIH trials of 67 anti-tumor products approved by the Food and Drug Administration between 2018 and 2023 and found that the "3 + 3" design remains the predominant dose-escalation method (66.2%). The number of patients receiving sub-therapeutic doses is positively correlated with the maximum tolerated dose (MTD) or maximum dose (MD) to starting dose ratio (P = 0.056) and the number of dose levels in trials (P < 0.001). In addition, the proportion of products with a high ratio in antibody drugs is higher than that in small molecules (P < 0.001). The MTD or MD exceeded the label dose by three or more doses in 22.03% of the products. In conclusion, optimizing the starting dose selection method, refining the way of determining doses, and finding alternative indicators to replace toxicity as the endpoints will increase the effectiveness and broaden the beneficiary scope.

Pharmacokinetics of single dose administration of three increasing doses of acetaminophen per os in 1-3-month-old foals

BACKGROUND

Acetaminophen is a common analgesic and antipyretic drug used in human medicine and might be an alternative to nonsteroidal anti-inflammatory drugs for treating pain and pyrexia in foals. The pharmacokinetics and safety of differing doses of acetaminophen have not been investigated in foals.

OBJECTIVES

To determine the plasma pharmacokinetics and any changes in haematology and biochemistry profiles following oral administration of single doses of acetaminophen at 10, 20, and 40 mg/kg to foals.

STUDY DESIGN

Randomised cross-over pharmacokinetic study.

METHODS

Six Quarter Horse (two colts and four fillies) foals received 10, 20, and 40 mg/kg acetaminophen orally once. Haematology and biochemistry profiles were performed before and 7 days after each drug administration. Blood samples were collected over 64 h after drug administration and were used to quantify plasma acetaminophen concentrations by liquid chromatography. Pharmacokinetic parameters were determined using compartmental analysis.

RESULTS

Median (range) acetaminophen plasma concentrations were 4.4 (1.8-5.1), 6.3 (2.6-12.6), and 14 (7.3-18) μg/ml for the 10, 20, and 40 mg/kg doses, respectively. Median acetaminophen area under the concentration versus time curve (AUC)0-∞ ranged from 25 (11-32), 41 (22-74), and 105 (82-142) h × μg/ml for the 10, 20, and 40 mg/kg doses, respectively. Dose-normalised maximal concentrations and AUC0-∞ values were similar across dose concentrations (p > 0.05). Median terminal half-life for all doses was 2.7-2.8 h. Haematology and biochemistry profiles were normal except for blood urea nitrogen and alkaline phosphatase concentrations.

MAIN LIMITATIONS

Foals were growing throughout the study, starting at 1 month and ending at 3 months. Deposition of drugs changes with age. The sample size was small and only single doses were evaluated. No liver biopsies were performed.

CONCLUSION

Plasma disposition of acetaminophen after a single oral dose of 10, 20, and 40 mg/kg to 1-3-month-old foals varies greatly with the dose. The analgesic and antipyretic effect in foals is unknown.

Clinical Trials Overview: From Explanatory to Pragmatic Clinical Trials

Clinical trials have been the bedrock of research to evaluate the safety and efficacy of new medical, surgical, or other interventions. Traditional "explanatory" clinical trials have aimed to explain a biological cause (new treatment) and effect (patient outcome) while controlling for many factors that might impact the evaluation, such as restricted eligibility criteria, frequent follow-up visits, and multiple clinical and laboratory measures. Despite the benefits of a well-controlled clinical trial, compromises have been made that can limit who might benefit from a new intervention, can increase complexity of the conduct of a trial, or that lead to excessively long durations of trials. An alternative approach to evaluate the effectiveness of an intervention is based on "pragmatic" clinical trials, which consider how an intervention affects a patient's condition in the real world, accounting for how to optimize an intervention within the operations of busy and diverse clinical practices. Although we describe explanatory and pragmatic trial designs as separate approaches, there is a continuum of approaches that intersect. Some key points are the need to maintain scientific rigor, increase efficiency of clinical trials operations, ensure that trial results can be generalized to a broad spectrum of patients, and balance the needs of real-world clinical care. Pragmatic trials can leverage technology and telecommunication strategies of decentralized trials to further reach underrepresented and underserved patients to close the health disparity gaps.

To blind or not to blind first in human and exploratory clinical trials: Acceleration of development vs. risk of bias

An IQ consortium working group (WG) conducted a survey across multiple biopharmaceutical companies to gain information about the level of blinding commonly utilized for early clinical development trials. The main objectives were: (1) to understand blinding practices between healthy volunteer (HV) and early explorative patient trials in all therapeutic areas except oncology where early clinical trials are commonly open‐label; (2) to understand the rationale for blinding/unblinding practices; (3) to understand the groups and personnel involved in unblinding; and (4) strategic considerations around blinding/unblinding options in early clinical development trials—risk of bias vs. potential for acceleration. A survey containing 31 main questions with additional sub‐clarifying questions was conducted. Sixteen large and mid‐size pharmaceutical companies responded. Responses were aligned across functions within each participating company. Additional information was gathered at an American Association of Pharmaceutical Scientists (AAPS) webinar with polling options to roughly 550 registered attendees to evaluate the reason for the unblinding decisions. The results revealed divergence across companies in the blinding approaches most commonly applied but with some study types, there were clearly favored options. Based on these results, the WG developed strategic considerations for first‐in‐human HV trials and nonpivotal explorative trials in patients. This paper should facilitate discussions among various clinical development functions, such as Clinical Pharmacology, Statistics, Clinical, Bioanalytics, and Regulatory Functions. Such discussions on study design and operations are warranted to allow implementation of more flexible blinding approaches to accelerate data driven decisions in drug development and allow earlier access of patients to needful medicines.

Reexamining Ophthalmic Drugs, Safety and Tolerability in Phase 1 Clinical Trials

Purpose

The purpose of this study was to evaluate the safety and tolerability profile of drugs used for treating common eye disorders when applied to normal healthy volunteers (NHVs) as explored in phase 1 trials.

Subjects and Methods

A total of 166 NHVs were identified in six phase 1 trials, examined in a retrospective analysis. The primary endpoints were visual comfort (by ocular comfort index, OCI) and safety (laboratory evaluations, vital signs (VS), visual acuity (VA), intraocular pressure (IOP), lissamine green and fluorescein staining, conjunctival hyperemia, chemosis, and adverse events’ incidence (AE)).

Results

Compared to baseline, 75.9%, 40.4% and 73.7% of NHV (for lubricant, hypotensive and antibiotic treatments, respectively) improved their OCI score by their final visit. Laboratory evaluations and VS were within normal ranges in 88% of NHV. Similar results were found for VA, corneal and conjunctival staining, and chemosis. IOP decreased significantly in the hypotensive agents’ group, trace to mild hyperemia was reported in 32.1%, 27.1%, and 6.8%, respectively. Additionally, lubricant and hypotensive investigational drugs (ID) had a lower risk of incidence of AE than approved drugs (OR 0.856, 95% CI [0.365, 1.999] and 0.636, 95% CI [0.096, 4.197], respectively). Meanwhile, on antibiotic drugs, the risk for ID-related AE was higher (OR 1.313, 95% CI [0.309, 5.583]).

Conclusion

Phase 1 trials are important in order to ensure the safety and tolerability of ophthalmic medications. This study demonstrates that NHVs do not face a significant risk of harm in these studies, since 98% of the reported AE were mild, and all AE were resolved by the end of the study in which they appeared.

Trial Registration

This is a retrospective study of six previously conducted clinical trials, registered on clinicaltrials.gov with the following registration IDs: NCT04081610, NCT03524157, NCT03520348, NCT03966365, NCT03965052 and, NCT03519516.

A Single Animal Species-Based Prediction of Human Clearance and First-in-Human Dose of Monoclonal Antibodies: Beyond Monkey

These days, there is a lot of emphasis on the prediction of human clearance (CL) from a single species for monoclonal antibodies (mabs). Many studies indicate that monkey is the most suitable species for the prediction of human clearance for mabs. However, it is not well established if rodents (mouse or rat) can also be used to predict human CL for mabs. The objectives of this study were to predict and compare human CL as well as first-in-human dose of mabs from mouse or rat, ormonkey. Four methods were used for the prediction of human CL of mabs. These methods were: use of four allometric exponents (0.75, 0.80, 0.85, and 0.90), a minimal physiologically based pharmacokinetics method (mPBPK), lymph flow rate, and liver blood flow rate. Based on the predicted CL, first-in-human dose of mabs was projected using either exponent 1.0 (linear scaling) or exponent 0.85, and human-equivalent dose (HED) from each of these species. The results of the study indicated that rat or mouse could provide a reasonably accurate prediction of human CL as well as first-in-human dose of mabs. When exponent 0.85 was used for CL prediction, there were 78%, 95%, and 92% observations within a 2-fold prediction error for mouse, rat, and monkey, respectively. Predicted human dose fell within the observed human dose range (administered to humans) for 10 out of 13 mabs for mouse, 11 out of 12 mabs for rat, and 12 out of 15 mabs for monkey. Overall, the clearance and first-in-human dose of mabs were predicted reasonably well by all three species (a single species). On average, monkey may be the best species for the prediction of human clearance and human dose but mouse or rat especially; rat can be a very useful species for conducting the aforementioned studies.

First-in-Human Study to Assess the Safety, Tolerability, and Pharmacokinetics of Pirepemat, a Cortical Enhancer, in Healthy Volunteers

Pirepemat (IRL752) is a cortical enhancer being developed for the prevention of falls in patients with Parkinson disease. This first-in-human, randomized, double-blind, placebo-controlled phase 1 study evaluated safety, tolerability, and pharmacokinetics (PK) of pirepemat administered as oral single ascending doses (10, 35, 75, 175, 350 mg) and multiple ascending doses (100 and 250 mg 3 times daily) for 7 days to healthy male volunteers. Twenty and 24 subjects were randomly assigned in the single ascending dose and multiple ascending doses parts of the study, respectively. Pirepemat was generally well tolerated, although an increased frequency of adverse events of mild intensity within nervous system disorders (headache and dizziness) was seen after administration of 350 mg as a single dose and after multiple doses of 100 and 250 mg. PK of pirepemat showed a linear relationship over the dose range studied and exhibited dose proportionality after multiple-dose administration. Accumulation after 7 days of multiple dosing was minor. Absorption was rapid, with a median time to maximum concentration of 2.0 hours on day 1 and day 7 (100 and 250 mg) and a mean terminal half-life between 3.7 and 5.2 hours. Food intake had no (obvious) impact on PK. The results support 3-times-daily dosing and further clinical development.

Phase 1 Clinical Trials of Small Molecules: Evolution and State of the Art

BACKGROUND

Phase 1 studies comprise the first exposure of a promising new chemical entity in healthy volunteers or, when appropriate, in patients. To assure a solid foundation for subsequent drug development, this first step must carefully assess the safety and tolerance of a new compound and often provide some indication of potential effect, so that a safe dose or dose range can be confidently selected for the initial Phase 2 efficacy study in the target patient population.

METHODS

This review was based on a literature search using both Google Scholar and PubMed, dated back to 1970, using search terms including "healthy volunteers", "Phase 1", and "normal volunteers", and also based on the authors' own experience conducting Phase 1 clinical trials. This paper reviews the history of Phase 1 studies of small molecules and their rapid evolution, focusing on the critical single and multiple dose studies, their designs, methodology, use of pharmacokinetic and pharmacodynamic modeling, application of potentially helpful biomarkers, study stopping criteria, and novel study designs.

RESULTS

We advocate for determining the safe dose range of a new compound by conducting careful dose escalation in a well-staffed inpatient setting, defining the maximally tolerated dose (MTD) by reaching the minimally intolerated dose (MID). The dose immediately below the MID is then defined as the MTD. This is best accomplished by using appropriately screened patients for the target indication, as patients in many CNS indications often tolerate doses differently than healthy non-patients. Biomarkers for safety and pharmacodynamic measures can also assist in further defining a safe and potentially effective dose range for subsequent clinical trial phases.

CONCLUSION

Phase 1 studies can yield critical insights into the pharmacology of a new compound in man and offer perhaps the only development period in which the dose range can be safely and thoroughly explored. Phase 1 studies often contain multiple endpoint objectives, the reconciliation of which can present a dilemma for drug developers and study investigators alike, but which can crucially determine whether a compound can survive to the next step in the drug development process.

Plasma disposition of gabapentin after the intragastric administration of escalating doses to adult horses

Background

In humans, gabapentin an analgesic, undergoes non‐proportional pharmacokinetics which can alter efficacy. No information exists on the pharmacokinetics of dosages >20 mg/kg, escalating dosages or dose proportionality of gabapentin in horses.

Hypothesis and Objectives

Gabapentin exposure in plasma would not increase proportionally relative to the dose in horses receiving dosages ≥20 mg/kg. To assess the plasma pharmacokinetics of gabapentin after nasogastric administration of gabapentin at dosages of 10 to 160 mg/kg in adult horses.

Animals

Nine clinically healthy adult Arabian and Quarter Horses.

Methods

In a randomized blinded trial, gabapentin was administered by nasogastric intubation to horses at 10, 20 mg/kg (n = 3) and 60, 80, 120, 160 mg/kg (n = 6). Plasma was collected before and at regular times over 64 hours after administration of gabapentin. Gabapentin was quantified using a validated chromatographic method. Dose proportionality was estimated using a power model. Pharmacokinetic parameters were estimated using compartmental pharmacokinetic analysis.

Results

Plasma pharmacokinetics parameters of gabapentin were estimated after nasogastric administration at dosages of 10 to 160 mg/kg. Gabapentin plasma concentration increased with dose increments. However, the area under the concentration curve from zero to infinity and maximal plasma concentration did not increase proportionally relative to the dose in horses.

Conclusions and Clinical Importance

Gabapentin exposure in plasma is not proportional relative to the dose in horses receiving nasogastric dosages of 10 to 160 mg/kg.

Randomized, double-blind, placebo-controlled phase I dose escalation study of Dan Qi Tong Mai tablet in healthy volunteers

BACKGROUND

This study aims to assess the tolerability and safety of DQTM tablet, which contains a complex mixture of Salvia miltiorrhiza salvianolic acids and Panax notoginseng saponins.

METHODS

A double-blind, randomized, placebo-controlled phase I dose escalation study was conducted in 84 healthy volunteers. In a single ascending dose study, active ingredients were administered in various doses (90, 270, 540, 1080, 1800, 2880, 4320 or 5760 mg) to 60 subjects in cohorts 1-8. In a multiple ascending dose study, active ingredients were administered at doses of 360, 720 or 2160 mg twice daily to 24 subjects in cohorts 9-11 for 14 consecutive days. Safety was evaluated based on clinical symptoms, vital signs, physical examinations, electrocardiography, laboratory tests and adverse events.

RESULTS

No serious adverse events or clinically significant changes in vital signs or electrocardiography were observed. One subject experienced mildly elevated levels of alanine aminotransferase and aspartate transaminase but recovered spontaneously. Five subjects experienced a small increase in the number of daily stools.

CONCLUSIONS

DQTM tablet was well tolerated at single doses of up to 5760 mg and twice-daily doses of up to 2160 mg for 14 consecutive days. The most frequent adverse event was an increase in the number of daily stools.

The Case for an Unblinded Modeler in Early Clinical Development

The current trend for clinical pharmacology is toward more complex studies (eg, umbrella protocols covering single and multiple ascending doses, food effect, metabolism pathways), requiring many decisions to be made during their conduct. This article discusses guidance of such early clinical studies by modeling and simulation. The ability to make use of all available information each time new data become available during the study requires the modeling scientist to be unblinded. This must of course not jeopardize the blinding of the clinical team, and this article discusses how unblinding can be prevented. Although modeling and simulation are established for guidance of the drug development process overall, they are not frequently used for guidance on a small scale, that is, during studies with the largest uncertainty, the first-in-human studies. Application of a quantitative model backbone makes early clinical drug development a more efficient process and provides additional safety for healthy subjects and patients. Real clinical impact is illustrated by 3 case studies that show different contributions from unblinded modeling: dose escalation based on safety data, modeling and predicting with explicit incorporation of in vitro data, and dose escalation supported by unblinded analysis of adverse event data, which resulted in new insights of the clinical team without being unblinded and made it possible to proceed with dose escalation and to extend the study with an up-titration group.

Nasal administration of the neuroprotective candidate NeuroEPO to healthy volunteers: a randomized, parallel, open-label safety study

BACKGROUND

Delivery of therapeutic agents as erythropoietin (EPO) into Central Nervous System through intranasal route could benefit patients with neurological disorders. A new nasal formulation containing a non-hematopoietic recombinant EPO (NeuroEPO) has shown neuroprotective actions in preclinical models. In the current study, the safety of NeuroEPO was evaluated for the first time in humans.

METHODS

A phase I, randomized, parallel, open-label study was carried out in healthy volunteers. They received, intranasally, 1 mg of NeuroEPO every 8 h during 4 days (Group A) or 0.5 mg of NeuroEPO (Group B) with the same schedule. The working hypothesis was that intranasal NeuroEPO produce <10% of severe adverse reactions in the evaluated groups. Therefore, a rigorous assessment of possible adverse events was carried out, which included tolerance of the nasal mucosa and the effect on hematopoietic activity. Clinical safety evaluation was daily during treatment and laboratory tests were done before and on days 5 and 14 after starting treatment.

RESULTS

Twenty-five volunteers, 56% women, with a mean age of 27 yrs. were included. Twelve of them received the highest NeuroEPO dose. Twenty types of adverse events occurred, with headache (20%) and increase of hepatic enzymes (20%) as the most reported ones. Nasopharyngeal itching was the most common local event but only observed in four patients (16%), all of them from the lowest dose group. About half of the events were very probably or probably caused by the studied product. Most of the events were mild (95.5%), did not require treatment (88.6%) and were completely resolved (81.8%). No severe adverse events were reported. During the study the hematopoietic variables were kept within reference values.

CONCLUSIONS

NeuroEPO was a safe product, well tolerated at the nasal mucosa level and did not stimulate erythropoiesis in healthy volunteers.

TRIAL REGISTRATION

Cuban Public Registry of Clinical Trials RPCEC00000157 , June 10, 2013.

Bayesian adaptive designs in single ascending dose trials in healthy volunteers

AIM

Recent publications indicate a strong interest in applying Bayesian adaptive designs in first time in humans (FTIH) studies outside of oncology. The objective of the present work was to assess the performance of a new approach that includes Bayesian adaptive design in single ascending dose (SAD) trials conducted in healthy volunteers, in comparison with a more traditional approach.

METHODS

A trial simulation approach was used and seven different scenarios of dose-response were tested.

RESULTS

The new approach provided less biased estimates of maximum tolerated dose (MTD). In all scenarios, the number of subjects needed to define a MTD was lower with the new approach than with the traditional approach. With respect to duration of the trials, the two approaches were comparable. In all scenarios, the number of subjects exposed to a dose greater than the actual MTD was lower with the new approach than with the traditional approach.

CONCLUSIONS

The new approach with Bayesian adaptive design shows a very good performance in the estimation of MTD and in reducing the total number of healthy subjects. It also reduces the number of subjects exposed to doses greater than the actual MTD.

A deviation from standard design? Clinical trials, research ethics committees, and the regulatory co-construction of organizational deviance

Focusing on the high-profile drug disaster at London's Northwick Park Hospital in 2006, this article explores how such an event can be seen as an example of organizational deviance co-constructed between the company running the research and the research ethics committee which approved the trial. This deviance was the result of the normalization of a specific dosing practice in the broader regulatory field, allowing the researchers and regulators to take a risky dosing strategy for granted as best practice. Drawing on the work of Diane Vaughan, this article uses interview data with researchers and members of the research ethics committee concerned as well as documentary material, to show how work group cultures between regulators and those they are intended to oversee are maintained, and how the culturally embedded assumptions of such work groups can result in organizational and regulatory deviance.

Use of functional imaging across clinical phases in CNS drug development

The use of novel brain biomarkers using nuclear magnetic resonance imaging holds potential of making central nervous system (CNS) drug development more efficient. By evaluating changes in brain function in the disease state or drug effects on brain function, the technology opens up the possibility of obtaining objective data on drug effects in the living awake brain. By providing objective data, imaging may improve the probability of success of identifying useful drugs to treat CNS diseases across all clinical phases (I-IV) of drug development. The evolution of functional imaging and the promise it holds to contribute to drug development will require the development of standards (including good imaging practice), but, if well integrated into drug development, functional imaging can define markers of CNS penetration, drug dosing and target engagement (even for drugs that are not amenable to positron emission tomography imaging) in phase I; differentiate objective measures of efficacy and side effects and responders vs non-responders in phase II, evaluate differences between placebo and drug in phase III trials and provide insights into disease modification in phase IV trials.

Animal models and conserved processes

BACKGROUND

The concept of conserved processes presents unique opportunities for using nonhuman animal models in biomedical research. However, the concept must be examined in the context that humans and nonhuman animals are evolved, complex, adaptive systems. Given that nonhuman animals are examples of living systems that are differently complex from humans, what does the existence of a conserved gene or process imply for inter-species extrapolation?

METHODS

We surveyed the literature including philosophy of science, biological complexity, conserved processes, evolutionary biology, comparative medicine, anti-neoplastic agents, inhalational anesthetics, and drug development journals in order to determine the value of nonhuman animal models when studying conserved processes.

RESULTS

Evolution through natural selection has employed components and processes both to produce the same outcomes among species but also to generate different functions and traits. Many genes and processes are conserved, but new combinations of these processes or different regulation of the genes involved in these processes have resulted in unique organisms. Further, there is a hierarchy of organization in complex living systems. At some levels, the components are simple systems that can be analyzed by mathematics or the physical sciences, while at other levels the system cannot be fully analyzed by reducing it to a physical system. The study of complex living systems must alternate between focusing on the parts and examining the intact whole organism while taking into account the connections between the two. Systems biology aims for this holism. We examined the actions of inhalational anesthetic agents and anti-neoplastic agents in order to address what the characteristics of complex living systems imply for inter-species extrapolation of traits and responses related to conserved processes.

CONCLUSION

We conclude that even the presence of conserved processes is insufficient for inter-species extrapolation when the trait or response being studied is located at higher levels of organization, is in a different module, or is influenced by other modules. However, when the examination of the conserved process occurs at the same level of organization or in the same module, and hence is subject to study solely by reductionism, then extrapolation is possible.

A brief survey of first-in-human studies

First-in-human (FIH) studies are a critical step in the drug development process and typically aim to characterize a compound's pharmacokinetics, potential effective concentration or dose, and safety or tolerability margins. Although effort continues to enhance the predictive quality of the selection of FIH doses from preclinical data, and little consensus is available on the design and conduct of FIH studies, detailed surveys describing general approaches taken in FIH studies are useful in the optimization of early-phase clinical drug development. Although allometric scaling techniques continue to provide poor predictive estimates for human pharmacokinetic parameters, FIH starting doses are selected with substantial safety factors applied to human equivalent dose, often in excess of regulatory guidelines. Based on these examples, it appears that relatively conservative 2-fold dose escalations are the most common escalation approach within FIH single ascending dose studies. The combination of conservative dose escalations with low starting doses can result in large FIH trials, consuming both time and resources. Approaches that could enhance the predictive nature of a compound's disposition and adaptive nature of FIH studies could provide a tremendous benefit for drug development.

Toxicity-evaluation designs for phase I/II cancer immunotherapy trials

OBJECTIVES

To facilitate more efficient Phase I/II cancer immunotherapy trials by incorporating statistically rigorous safety analysis.

SETTING

The standard Phase I oncology trial is designed to find the maximum tolerated dose (MTD) in a setting where serious drug-related toxicity is expected. However, many newer agents hope to show the efficacy without increasing the background rate of adverse events. Formal statistical designs in this setting are needed.

RESULTS

The Phase I/II toxicity-evaluation design is suitable when the therapeutic dose is expected to be well below the MTD. In Phase I, the design enrolls multiple cohorts at the target dose, possibly after an initial dose titration stage, and tests a formal safety hypothesis using a standard 3 + 3 enrollment scheme. Phase I serves as an interim safety analysis before proceeding to Phase II efficacy testing. We give an exact upper confidence limit on the toxicity rate at the therapeutic dose using the combined Phase I/II toxicity data, as well as the maximum likelihood estimate of the toxicity rate. We describe an example where the design has been used for a Phase I/II trial of immunotherapy in leukemia.

CONCLUSIONS

Phase I/II toxicity-evaluation designs are simple to execute and may be suitable for some cancer immunotherapy trials. We show how to compute power, expected sample size, and expected number of dose-limiting toxicities, as well as the maximum likelihood estimator and exact small sample confidence intervals for the toxicity rate at the therapeutic dose. More flexible designs are briefly discussed.

Healthy volunteers and early phases of clinical experimentation

The main goal of early phase trials is to gain knowledge about the clinical suitability of novel compounds, without pursuing specific therapeutic purposes. Healthy volunteers usually represent the ideal model for conducting phase I clinical trials, in order to investigate pharmacokinetics and pharmacodynamics as well as to document safety and tolerability without interference by concomitant pathological conditions. The increasing cost of novel drug development, in conjunction with ethical considerations, has fostered a new procedure for first-in-man trials, designated as "phase 0," which is conducted very early on a limited number of healthy volunteers who are exposed to low drug levels. The present review discusses issues concerning the enrollment of healthy volunteers in the early phase of drug development from different points of view, with some focus on the Italian experience. From the ethical standpoint, much discussion revolves around payments to healthy volunteers. Most authors agree that an adequate remuneration must be provided to healthy subjects, while avoiding coercion and excessive psychological pressure. Pending the lack of international and national guidelines, our center for clinical drug experimentation has implemented an operative procedure to estimate payments for healthy volunteers based on specific items, including restriction, time spent, discomfort, and risk. Other unresolved issues about the recruitment of healthy volunteers are represented by the lack of international consensus on the definition of healthy status and the need for guidelines about advertisement on clinical trials addressed to potential participants.

An adaptive design for identifying the dose with the best efficacy/tolerability profile with application to a crossover dose-finding study

Proof-of-concept in clinical trials has traditionally focused on the identification of a maximum tolerated dose with the assumption that the higher doses provide better efficacy. However, adverse events associated with a maximum tolerated dose may have a negative effect on efficacy. We present an efficient adaptive dose-finding strategy that concentrates patient assignments at and around the dose which has the best efficacy/tolerability profile based on a utility function. The strategy is applied within the setting of a crossover design. While the strategy may also be applied to parallel studies, a crossover design provides more power for a given sample size for comparisons between the optimal dose versus placebo and/or active control when it is reasonable to assume no carryover effects.

Evaluation of agile designs in first-in-human (FIH) trials--a simulation study

The aim of the investigation was to evaluate alternatives to standard first-in-human (FIH) designs in order to optimize the information gained from such studies by employing novel agile trial designs. Agile designs combine adaptive and flexible elements to enable optimized use of prior information either before and/or during conduct of the study to seamlessly update the study design. A comparison of the traditional 6 + 2 (active + placebo) subjects per cohort design with alternative, reduced sample size, agile designs was performed by using discrete event simulation. Agile designs were evaluated for specific adverse event models and rates as well as dose-proportional, saturated, and steep-accumulation pharmacokinetic profiles. Alternative, reduced sample size (hereafter referred to as agile) designs are proposed for cases where prior knowledge about pharmacokinetics and/or adverse event relationships are available or appropriately assumed. Additionally, preferred alternatives are proposed for a general case when prior knowledge is limited or unavailable. Within the tested conditions and stated assumptions, some agile designs were found to be as efficient as traditional designs. Thus, simulations demonstrated that the agile design is a robust and feasible approach to FIH clinical trials, with no meaningful loss of relevant information, as it relates to PK and AE assumptions. In some circumstances, applying agile designs may decrease the duration and resources required for Phase I studies, increasing the efficiency of early clinical development. We highlight the value and importance of useful prior information when specifying key assumptions related to safety, tolerability, and PK.

Exploratory assessment of dose proportionality: review of current approaches and proposal for a practical criterion

This article reviews currently used approaches for establishing dose proportionality in Phase I dose escalation studies. A review of relevant literature between 2002 and 2006 found that the power model was the preferred choice for assessing dose proportionality in about one-third of the articles. This article promotes the use of the power model and a conceptually appealing extension, i.e. a criterion based on comparing the 90% confidence interval for the ratio of predicted mean values from the extremes of the dose range (R(dnm)) to pre-defined equivalence criterion (theta(L),theta(U)). The choice of bioequivalence default values of theta(L)=0.8 and theta(U)=1.25 seems reasonable for dose levels only a doubling apart but are impractically strict when applied over the complete dose range. Power calculations are used to show that this prescribed criterion lacks power to conclude dose proportionality in typical Phase I dose-escalation studies. A more lenient criterion with values theta(L)=0.5 and theta(U)=2 is proposed for exploratory dose proportionality assessments across the complete dose range.

First-in-Man (FIM) clinical trials post-TeGenero: a review of the impact of the TeGenero trial on the design, conduct, and ethics of FIM trials

A recent first time in man (FIM) trial of an "immuno modulator" compound (TGN1412) resulted in unprecedented toxicity. Since this occurred in 2006 a widely publicized scientific debate, as well as a controversy in the lay community has examined the principle of design and content of the study as well as the concept of FIM studies. This paper reviews the controversy, analyzes the problems of the TGN1412 trial and FIM trials in general and the reaction of the lay and scientific communities. Difficulties in these high risk trials is highlighted and possible design and execution procedural improvements are recommended. Consideration is given to the ethical debate regarding participation of normal, healthy research volunteers in FIM studies. The role of monetary incentive(s) is discussed as well as the opposition of many participants in this debate on financial compensation of volunteers for the assumption of risk and the need to adopt a no-fault scheme that fairly compensates injured trial participants.FIM studies are critical for the development of new therapeutic agents. Improving trial design and execution and fairly compensating volunteers will facilitate these studies, enhance equity and thus provide an ethical basis for continuing FIM studies that may pose a serious risk to participants, a risk that society needs taken for the development of needed therapeutic agents.

Integrated pharmacokinetics and pharmacodynamics in drug development

Drug development is a complex, lengthy and expensive process. Pharmaceutical companies and regulatory authorities have recognised that the drug development process needs optimisation for efficiency in view of the return on investments. Pharmacokinetics and pharmacodynamics are the two main principles determining the relationship between dose and response. This article provides an update on integrated approaches towards drug development by linking pharmacokinetics, pharmacodynamics and disease aspects into mathematical models. Gradually, a transition is taking place from a rather empirical approach towards a modelling- and simulation-based approach to drug development. The main learning phases should be phases 0, I and II, whereas phase III studies should merely have a confirmatory purpose. In model-based drug development, mechanism-based mathematical models, which are iteratively refined along the path of development, incorporate the accumulating knowledge of the investigational drug, the disease and their mutual interference in different subsets of the target population. These models facilitate the design of the next study and improve the probability of achieving the projected efficacy and safety endpoints. In this article, several theoretical and practical aspects of an integrated approach towards drug development are discussed, together with some case studies from different therapeutic areas illustrating the application of pharmacokinetic/pharmacodynamic disease models at different stages of drug development.

A brief review of Phase 1 and Clinical Pharmacology statistics in clinical drug development

Following a brief description of historical Phase 1 research, Clinical Pharmacology studies, and the role of statistics in this setting, Phase 1 study design and statistical analysis are reviewed. A description of design and analysis for Clinical Pharmacology studies is also provided, and the role of statistics in this area of drug development in the future is discussed. While challenging, this area of statistics in drug development is likely to have an active and engaging future.

Tolerability, pharmacokinetics, and pharmacodynamics of clazosentan, a parenteral endothelin receptor antagonist

OBJECTIVE

The purpose of this study was to investigate in healthy male subjects the tolerability, pharmacokinetics, and pharmacodynamics of ascending doses of clazosentan, an intravenous endothelin receptor antagonist.

METHODS

Clazosentan was infused at doses of 3-60 mg/h for 3 h, 60 mg/h for 6 h and at 30 mg/h for 12 h. Each dose was given to a separate group of subjects, six of whom received clazosentan and two placebo. Vital signs, ECG, adverse events, and clinical laboratory variables were monitored to assess tolerability. Blood and urine samples were collected frequently for pharmacokinetic and pharmacodynamic determinations.

RESULTS

Infusion of clazosentan up to doses of 30 mg/h for 3 h was well tolerated. A dose of 60 mg/h and longer infusions were less well tolerated and three subjects did not complete the 12-h infusion of 30 mg/h due to adverse events. Headache was the most commonly reported adverse event followed by nausea, vomiting, and nasal congestion. The pharmacokinetics of clazosentan were dose proportional in the dose range investigated. Values (mean and 95% confidence intervals) for clearance and volume of distribution at a dose of 10 mg/h for 3 h were 42.2 (36.6, 48.7) l/h and 32.4 (27.0, 38.8) l, respectively. Both variables were independent of dose. The elimination of clazosentan was characterized by a very rapid disposition phase with a half-life of 6-10 min. Compared to baseline, endothelin-1 concentrations increased approximately 2-fold after infusion of clazosentan but no dose-dependent relationship could be discerned for this effect.

CONCLUSION

The observed tolerability, pharmacokinetic, and pharmacodynamic profile warrant further clinical development of clazosentan at lower doses.