Posaconazole: A Review of the Gastro-Resistant Tablet and Intravenous Solution in Invasive Fungal Infections

Cost-Effectiveness of Posaconazole vs. First-Generation Triazoles for the Prevention of Invasive Fungal Infections Among High-Risk Patients With Hematological Malignancies in China

Background

Posaconazole is confirmed to be more effective for preventing invasive fungal infections (IFIs) than first-generation triazoles (fluconazole and itraconazole), but its economic value has not been comprehensively evaluated in China. This study compared the cost-effectiveness of these two antifungal prophylaxis regimens in hematological-malignancy patients at high risk for IFIs from the Chinese healthcare perspective.

Methods

A hybrid decision tree and Markov model were built using published data to estimate the total costs and quality-adjusted life-years (QALYs) of antifungal prophylaxis with posaconazole oral suspension and first-generation triazoles. Regimens with an incremental cost-effectiveness ratio (ICER) lower than the threshold of willingness to pay (WTP) were considered cost-effective. One-way and probabilistic sensitivity analyses were performed to assess model robustness. The regional imbalance of economic development and the tablet formulation of posaconazole were considered in the scenario analyses.

Results

In the base-case analysis, posaconazole oral suspension provided an additional 0.109 QALYs at an incremental cost of $954.7, yielding an ICER of $8,784.4/QALY, below the national WTP threshold of $31,315/QALY. One-way and probabilistic sensitivity analyses showed that the results were robust. Scenario analyses showed that the base-case ICER was consistently below the WTP thresholds of all 31 Chinese provinces, with the likelihood of posaconazole being cost-effectiveness ranging from 78.1 to 99.0%. When the posaconazole oral suspension was replaced by the tablet formulation, the ICER increased to $29,214.1/QALY, still below the national WTP threshold and WTP thresholds of 12 provinces.

Conclusions

Posaconazole oral suspension is a highly cost-effective regimen for preventing IFI in high-risk hematological-malignancy patients from the Chinese healthcare perspective. Posaconazole tablets may also be considered in some high-income regions of China.

Evaluating posaconazole, its pharmacology, efficacy and safety for the prophylaxis and treatment of fungal infections

INTRODUCTION

Invasive fungal diseases (IFDs) are a significant cause of morbidity and mortality among immunocompromised patients. Safe and effective antifungal medications used for prophylaxis and treatment are pivotal in their management. Posaconazole is a promising triazole antifungal agent.

AREAS COVERED

The authors discuss the pharmacological properties of posaconazole, including pharmacokinetics/pharmacodynamics, safety and tolerability profile, together with efficacy data for prophylaxis and treatment as well as its use in special populations based on current literature.

EXPERT OPINION

Posaconazole has a favorable safety and tolerability profile; however, caution is advised when co-administered with agents that are CYP3A4 inhibitors, because their concentration may significantly increase, and their levels should be closely monitored. It has an extended spectrum of activity against yeasts and filamentous fungi. It is successfully used as prophylaxis for patients with acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) and post-hematopoietic cell transplantation (HCT) with graft-versus-host disease (GVHD). It is the first line treatment for oropharyngeal candidiasis and is also used as a salvage treatment for refractory IFDs. Currently available formulations include the oral suspension, delayed-release tablets and solution for intravenous infusion, all with different PK/PD properties and indications. Its use in children and adolescents is currently being examined in Phase-II clinical trials.

Pharmacological management of antifungal agents in pulmonary aspergillosis: an updated review

INTRODUCTION

Aspergillus may cause different types of lung infections: invasive, chronic pulmonary or allergic bronchopulmonary aspergillosis. Pharmacological management with antifungals poses as a challenge. Patients diagnosed with pulmonary aspergillosis are complex, as well as the problems associated with antifungal agents.

AREAS COVERED

This article reviews the pharmacology of antifungal agents in development and currently used to treat pulmonary aspergillosis, including the mechanisms of action, pharmacokinetics, pharmacodynamics, dosing, therapeutic drug monitoring and safety. Recommendations to manage situations that arise in daily clinical practice are provided. A literature search of PubMed was conducted on November 15^th, 2020 and updated on March 30^th, 2021.

EXPERT OPINION

Recent and relevant developments in the treatment of pulmonary aspergillosis have taken place. Novel antifungals with new mechanisms of action that extend antifungal spectrum and improve pharmacokinetic-related aspects, drug-drug interactions and safety are under current study. For those antifungals already marketed, new data related to pharmacokinetics, pharmacodynamics, dose adjustments in special situations, therapeutic drug monitoring and safety are available. To maximize efficacy and reduce the risk of associated toxicities, it is essential to choose the most appropriate antifungal; optimize its dose, interval, route of administration and length of treatment; and prevent side effects.

Evaluation of posaconazole plasma concentrations achieved with the delayed-release tablets in Korean high-risk patients with haematologic malignancy

BACKGROUND

Posaconazole (PCZ) is a triazole approved for prophylaxis of invasive fungal infections.

OBJECTIVES

Herein, the impact of clinical variables on PCZ plasma concentrations (PPCs) attained with PCZ delayed-release tablet (DRT) was investigated and compared with a historical cohort treated with PCZ oral suspension (OS).

PATIENTS/METHODS

Steady-state PCZ PPCs in 513 patients with haematologic malignancy treated with PCZ-DRT were assessed and impact of variables were analysed. Also, a comparison with matched historical cohort treated with PCZ-OS was made.

RESULTS

The median PPC in the PCZ-DRT group was 1,308.9 ng/mL (range: 29.8-10 455.9). Use of proton pump inhibitor (1181 vs 1344 ng/mL, P = .0337) in the AML/myelodysplastic syndrome remission induction group, diarrhoea (867 vs 1543 ng/mL, P = .0325) and gastrointestinal graft-versus-host disease (870 vs 1713 ng/mL, P = .0178) in the HSCT group were associated with lower PPCs. There was lack of evidence that hepatotoxicity was related with PCZ-DRT. Higher prevalence of UGT1A4*3 allele (33.0%) was noted compared to allele frequency in Koreans in those with PPCs < 500 mg/mL. The median PPC in the PCZ-DRT group was significantly higher than that in the PCZ-OS group (1308.9 vs 713.0 ng/mL, P < .0001). Significantly less patients had PPCs < 700 ng/mL in the PCZ-DRT group compared to the PCZ-OS group (18.7% vs 48.0%, P < .0001).

CONCLUSIONS

Our study demonstrates that PCZ-DRT has enhanced absorption and bioavailability than PCZ-OS in real-world clinical settings. In addition, specific factors associated with lower PPCs should prompt consideration of therapeutic drug monitoring in patients treated with PCZ-DRT.

Clinical Pharmacokinetics of Second-Generation Triazoles for the Treatment of Invasive Aspergillosis and Candidiasis

Second-generation triazoles were developed in response to the quest for more efficacious and safer therapeutic options for the treatment of severe systemic aspergillosis and candidiasis. These agents include voriconazole, posaconazole, isavuconazole, and ravuconazole. The aim of this review was to present and compare the pharmacokinetic characteristics of second-generation triazoles for the treatment of invasive aspergillosis and candidiasis, emphasizing their clinical implications. The MEDLINE, Scopus, EBSCO, Google Scholar, and SCIndeks databases were searched using advanced search options, including the names of second-generation triazoles and pharmacokinetic terms as keywords. The intravenous administration of voriconazole, posaconazole, and isavuconazole results in stable pharmacokinetics of these drugs, with mostly predictable variations influenced by common and usually known factors in routine clinical settings. The high oral bioavailability of isavuconazole and, to some extent, voriconazole makes them suitable for intravenous-to-oral switch strategies. Except for intravenous voriconazole (due to the accumulation of the toxic vehicle hydroxypropyl betadex), dose reduction of second-generation triazoles is not needed in patients with renal failure; patients with hepatic insufficiency require dose reduction only in advanced disease stages. The introduction of therapeutic drug monitoring could aid attempts to optimize the blood concentrations of triazoles and other drugs that are known to or that possibly interact, thus increasing treatment efficacy and safety. There is a need for new studies that are designed to provide useful data on second-generation triazole pharmacokinetics, particularly in special circumstances such as central nervous system and ocular infections, infections in newborns and infants, and in subjects with genetic polymorphisms of metabolizing enzymes.

Screening the in vitro susceptibility of posaconazole in clinical isolates of Candida spp. and Aspergillus spp. and analyzing the sequence of ERG11 or CYP51A in non-wild-type isolates from China

The present study was to determine the in vitro activity of posaconazole (POS) against 385 Candida and 268 Aspergillus clinical isolates from China. We found that POS was active against 85.5% Candida and 94.4% Aspergillus isolates. Non-wild-type (non-WT) phenotype was found in a subset of Candida albicans (15.4%), Candida tropicalis (11.9%), Aspergillus fumigatus (4.1%), and Aspergillus flavus (17.4%) isolates. Cross-resistance to POS and other triazoles was seen. Gene sequencing showed that 4 C. albicans, 1 C. tropicalis, and 9 A. fumigatus isolates with cross-resistance to POS and other triazoles had mutations in ERG11 or CYP51A. In conclusion, POS has potent in vitro activity against most of Candida and Aspergillus isolates from China. Non-WT phenotype and those with cross-resistance to POS and other triazoles exist, frequently driven by mutations of ERG11 in Candida spp. and CYP51A in Aspergillus spp.

Posaconazole oral dose and plasma levels in pediatric hematology-oncology patients

BACKGROUND

Posaconazole is a triazole with limited pharmacokinetic information in children. This study assessed the correlation between posaconazole oral solution daily dosage/kg/body weight and trough plasma level.

METHODS

A total of 97 hematology-oncology pediatric patients with ≥1 posaconazole plasma concentration level (PPC) assessment in the first 6 weeks after the start of posaconazole treatment were included.

RESULTS

Posaconazole was used as prophylaxis in 84 of 97 (87%) patients and as therapy in 13 of 97 (13%). The median daily dose/kg/bw ranged from 10 to 12 mg in the prophylaxis group and 12.5 to 16.5 mg in the therapy group. The median value of PPC for the prophylaxis group was 0.9 and 0.8 μg/mL at the first and second/third determinations, respectively. Posaconazole prophylaxis failed in 4 of 84 patients (5%). The median value of PPC for the therapy group was 1.5 and 1.4 μg/mL at the first/second and the third determination, respectively. Posaconazole-related side effects were reported in 6 patients and all regressed with the suspension of the drug. In the prophylaxis group, the use of proton-pump inhibitors was significantly associated with a lower PPC, P = 0.04.

CONCLUSIONS

Posaconazole may be a valuable antifungal agent in children despite the incomplete knowledge of its pharmacokinetic characteristics.

Cost-Effectiveness of Posaconazole Tablets for Invasive Fungal Infections Prevention in Acute Myelogenous Leukemia or Myelodysplastic Syndrome Patients in Spain

Introduction

Posaconazole is superior to fluconazole (FLU) and itraconazole (ITRA) in the prevention of invasive fungal diseases (IFDs) in neutropenic patients with acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS). A new tablet formulation of posaconazole with improved pharmacokinetic and pharmacodynamic properties compared to posaconazole oral solution has recently been approved. The objective of this study is to estimate the cost-effectiveness of the newly developed posaconazole tablets versus FLU oral suspension or ITRA oral solution for preventing IFDs in high-risk neutropenic patients with AML or MDS and from the perspective of the Spanish National Health System (NHS).

Methods

A previously validated economic model was used. The probabilities of experiencing an IFD, an IFD-related death or death from other causes over 100 days were based on clinical trial data and input into a decision tree. Surviving patients were entered into a Markov model to calculate total costs, number of IFDs and number of life-years gained per patient over a lifetime horizon in each disease and treatment group. Two health states, alive and dead, were considered. Health effects were discounted using a rate of 3%. Univariate and probabilistic sensitivity analyses were conducted.

Results

During the first 100 days, posaconazole tablets were associated with a lower risk of IFDs (0.046 vs. 0.111), longer life expectancy (2.92 vs. 2.69 years) and lower total costs (€5906.06 vs. €7847.20 per patient) over the patients’ lifetimes compared to FLU or ITRA treatments. Thus, posaconazole tablets were more effective and less costly than FLU or ITRA. Probabilistic sensitivity analysis indicated that there was a 79.9% probability of posaconazole tablets being cost-saving compared to FLU or ITRA.

Conclusion

From the Spanish NHS perspective, posaconazole tablets are cost-effective compared to FLU or ITRA in AML or MSD patients with chemotherapy-induced neutropenia and at high risk for IFDs.

Funding

MSD Sharp & Dohme.

Marked peripheral eosinophilia due to prolonged administration of posaconazole

Introduction. Posaconazole is a triazole antifungal that is used in the treatment of a variety of fungal infections, as well as in the management of mucormycosis (on an off-label basis). Eosinophilia associated with exposure to azole antifungals has been described rarely in the literature.

Case presentation. A 31-year-old male on peritoneal dialysis (PD) for end-stage renal disease, secondary to diabetic nephropathy, presented to hospital with abdominal pain after a trip to St Lucia. He was taken to the operating room, where the PD catheter was removed and an abdominal-wall abscess was debrided. Rhizopus species was recovered on culture of the abdominal-wall tissue, and the patient was started on amphotericin B deoxycholate. He was subsequently stepped down to posaconazole, for a planned treatment duration of 12 months. Approximately 43 days after the initiation of posaconazole, it was noted that his peripheral eosinophil count started to rise. No other cause for the eosinophilia was identified. Posaconazole was discontinued, and the patient’s eosinophil count began to drop 2 days later. The temporal association of eosinophilia following initiation of posaconazole and the subsequent improvement after drug discontinuation suggests a probable causal relationship.

Conclusion. At the time of writing, there have been only two other published cases of azole-associated peripheral eosinophilia. In reporting this case, we hope to increase health-care provider awareness of this rare adverse event. For patients receiving prolonged therapy with posaconazole, periodic monitoring of the complete blood count with differential may be considered.

Comparison of Plasma Concentrations of Posaconazole with the Oral Suspension and Tablet in Korean Patients with Hematologic Malignancies

The posaconazole tablet formulation was developed to have improved bioavailability compared to the oral suspension. Here, we compared posaconazole plasma concentration (PPC) with the posaconazole oral suspension versus the tablet in Korean patients undergoing remission induction chemotherapy for hematologic malignancies. PPC was measured at 3, 8, and 15 days of treatment with the oral suspension (174 patients) or the tablet (40 patients). At all time-points, mean PPC was significantly higher with the tablet compared to the oral suspension. Our findings suggest that posaconazole tablets generate an optimal PPC earlier and in more patients than the oral suspension among Korean patients.

Utilization of posaconazole oral suspension or delayed-released tablet salvage treatment for invasive fungal infection

Posaconazole may be useful for salvage treatment (ST) for invasive fungal infections (IFIs). The aim of this study was to evaluate the efficacy of posaconazole ST with either posaconazole oral suspension (SUS) or delayed-released tablet (TAB) in patients with IFI. A retrospective review of patients who received posaconazole ST for IFI at the University of Utah Health Sciences Center between December 2007 and March 2014 was conducted. A total of 14 episodes of posaconazole ST for proven (9 episodes) and probable (5 episodes) IFI were identified in 14 patients. The median age was 54 years and the majority of patients (64.3%) had underlying haematological diseases. Posaconazole SUS and TAB were used in 11 episodes and 3 episodes respectively. The duration of posaconazole ST ranged from 28 to 370 days with a median of 65 days. Posaconazole ST with TAB achieved favourable serum posaconazole trough concentrations (median 1.4 μg mL^-1 ) compared to posaconazole SUS (median 1.0 μg mL^-1 ). The overall clinical success rate with posaconazole ST was 71.4% (10 of 14 episodes). One patient died of progression of IFI. Adverse events were noted in two patients. Posaconazole SUS or TAB may be used effectively for IFI ST.

New facets of antifungal therapy

Invasive fungal infections remain a major cause of morbidity and mortality in immunocompromised patients, and such infections are a substantial burden to healthcare systems around the world. However, the clinically available armamentarium for invasive fungal diseases is limited to 3 main classes (i.e., polyenes, triazoles, and echinocandins), and each has defined limitations related to spectrum of activity, development of resistance, and toxicity. Further, current antifungal therapies are hampered by limited clinical efficacy, high rates of toxicity, and significant variability in pharmacokinetic properties. New antifungal agents, new formulations, and novel combination regimens may improve the care of patients in the future by providing improved strategies to combat challenges associated with currently available antifungal agents. Likewise, therapeutic drug monitoring may be helpful, but its present use remains controversial due to the lack of available data. This article discusses new facets of antifungal therapy with a focus on new antifungal formulations and the synergistic effects between drugs used in combination therapy.

Therapeutic Drug Monitoring of Posaconazole: an Update

Posaconazole is a second-generation triazole agent with a potent and broad antifungal activity. In addition to the oral suspension, a delayed-release tablet and intravenous formulation with improved pharmacokinetic properties have been introduced recently. Due to the large interindividual and intraindividual variation in bioavailability and drug-drug interactions, therapeutic drug monitoring (TDM) is advised to ensure adequate exposure and improve clinical response for posaconazole. Here, we highlight and discuss the most recent findings on pharmacokinetics and pharmacodynamics of posaconazole in the setting of prophylaxis and treatment of fungal infections and refer to the challenges associated with TDM of posaconazole.

Scedosporium apiospermum and S. prolificans mixed disseminated infection in a lung transplant recipient: An unusual case of long-term survival with combined systemic and local antifungal therapy in intensive care unit

Infections due Scedosporium spp. in lung transplant recipients are associated with disseminated disease with high mortality rates. The adjunctive local antifungal therapy may be a useful option when systemic treatment is insufficient and/or surgery is not feasible. We present a case of mixed disseminated infection due Scedosporium apiospermum and S. prolificans in a lung transplant recipient. Combined local and systemic antifungal therapy provided an unusual long-term survival in the intensive care unit.

Posaconazole plasma exposure correlated to intestinal mucositis in allogeneic stem cell transplant patients

PURPOSE

Low posaconazole plasma concentrations (PPCs) are frequently encountered in allogeneic hematopoietic stem cell transplant (HSCT) patients, due to variable gastrointestinal absorption. In this study, the impact of intestinal mucositis on posaconazole exposure is investigated.

PATIENTS AND METHODS

A prospective pharmacokinetic study was performed including allogeneic HSCT patients receiving posaconazole prophylaxis with the oral suspension or tablets. Steady state PPCs were determined using high-performance liquid chromatography-fluorescence detection at the day of transplantation (=day 0), day +7, and +14. Citrulline was measured using liquid chromatography-tandem mass spectrometry to evaluate severity of mucositis, at baseline (day -7 or -6), and at day 0, +7 and +14. Additionally, citrulline plasma concentrations and steady state trough PPCs were determined in hematological patients without HSCT or mucositis.

RESULTS

Thirty-four HSCT patients received posaconazole oral suspension together with 25 cL of Coca Cola, 6 HSCT patients received posaconazole tablets and 33 hematological patients not receiving HSCT received posaconazole oral suspension. The median (interquartile range) average PPC was 0.26 mg/L (0.17-0.43), 0.67 mg/L (0.27-1.38), and 1.08 mg/L (0.96-1.38), with suspension in HSCT patients, suspension in hematological patients and tablets in HSCT patients, respectively. A higher trough PPC was encountered with the oral suspension when citrulline plasma concentrations were above 10 μmol/L compared to values below 10 μmol/L (p < 0.001), whereas for tablets, average PPCs remained high with citrulline plasma concentrations below or above 10 μmol/L (p = 0.64).

CONCLUSION

Posaconazole tablets should be preferred to suspension in HSCT patients immediately after transplantation to prevent insufficient plasma exposure due to intestinal mucositis.

Supersaturation and Precipitation of Posaconazole Upon Entry in the Upper Small Intestine in Humans

The purpose of this study was to explore gastrointestinal dissolution, supersaturation and precipitation of the weakly basic drug posaconazole in humans, and to assess the impact of formulation pH and type on these processes. In a cross-over study, two posaconazole suspensions (40 mg dispersed in 240 mL water at pH 1.6 and pH 7.1, respectively) were intragastrically administered; subsequently, gastric and duodenal fluids were aspirated. In parallel, blood samples were collected. Additionally, posaconazole was intragastrically administered as a solution (20 mg in 240 mL water, pH 1.6). When posaconazole was administered as an acidified suspension, supersaturated duodenal concentrations of posaconazole were observed for approximately 45 min. However, extensive intestinal precipitation was observed. Administration of the neutral suspension resulted in subsaturated concentrations with a mean duodenal AUC0-120 min and Cmax being approximately twofold lower than for the acidified suspension. The mean plasma AUC0-8 h of posaconazole was also twofold higher following administration of the acidified suspension. Similar to the acidified suspension, significant intestinal precipitation (up to 92%) was observed following intragastric administration of the posaconazole solution. This study demonstrated for the first time the gastrointestinal behavior of a weakly basic drug administered in different conditions, and its impact on systemic exposure.

Posaconazole: An Update of Its Clinical Use

Posaconazole (PCZ) is a relatively new addition to the azole antifungals. It has fungicidal activities against Aspergillus fumigatus, Blastomyces dermatitidis, selected Candida species, Crytopcoccus neoformans, and Trichosporon. PCZ also has fungistatic activities against Candida, Coccidioides, selected Fusarium spp., Histoplasma, Scedosporium and Zygomycetes. In addition, combining the drug with caspofungin or amphotericin B results in a synergistic interaction against A. fumigatus, C. glabrata and C. neoformans. The absorption of PCZ suspension is enhanced when given with food, nutritional supplements, and carbonated beverages. Oral administration of PCZ in divided doses also increases its bioavailability. PCZ has a large volume of distribution and is highly protein bound (>95%). The main elimination route of PCZ is fecal. PCZ is an inhibitor of the CYP3A4 enzyme; therefore, monitoring for drug-drug interactions is warranted with other CYP3A4 substrates/inhibitors/inducers. The most common adverse effects include headache, fatigue, nausea, vomiting and elevated hepatic enzymes. PCZ, with its unique antifungal activities, expands the azole class of antifungal agents. Because of its limit in formulation, PCZ oral suspension is recommended in immunocompromised patients with functional gastrointestinaltracts who fail conventional antifungal therapies or who are suspected to have a breakthrough fungal infection. However, a delayed-release tablet formulation and intravenous (IV) injection became available in 2014, expanding the use of PCZ in other patient populations, including individuals who are unable to take oral formulations.

Prevention of invasive fungal infections in immunocompromised patients: the role of delayed-release posaconazole

Posaconazole is a triazole antifungal agent that has broad-spectrum activity against many yeasts and filamentous fungi, including Candida species, Cryptococcus neoformans, Aspergillus species, and Zygomycetes. This drug has been approved for the prevention of invasive fungal infections in patients with neutropenia and for the treatment of invasive fungal infections in hematopoietic stem cell transplant recipients with graft-versus-host disease. Studies on the clinical efficacy, safety, tolerability, and cost-effectiveness of posaconazole therapy were performed using the oral suspension form of the drug. Pharmacokinetic studies have found that the oral suspension form of posaconazole has problemeatic bioavailability: its absorption is affected by concomitant medication and food. This article discusses the pharmacokinetic properties of the newly developed posaconazole delayed-release tablet formulation and reviews the efficacy, safety, and cost-effectiveness of both the oral suspension and the new tablet formulation. In conclusion, the posaconazole tablet formulation has better systemic bioavailability, thereby enabling once-daily administration and better absorption in the presence of concomitant medication and food. However, well-designed clinical studies are needed to evaluate the use of the tablet formulation in real-life settings.

Advances in the treatment of invasive neonatal candidiasis

INTRODUCTION

Invasive candidiasis is responsible for ∼ 10% of nosocomial sepsis in very-low-birth-weight infants and is associated with substantial morbidity and mortality. Over the last two decades, the antifungal armamentarium against Candida spp. has increased; however, efficacy and safety studies in this population are lacking.

AREAS COVERED

We reviewed the medical literature and extracted information on clinical and observational studies evaluating the use of antifungal agents in neonates with invasive candidiasis.

EXPERT OPINION

Efficacy and safety data for antifungals in neonates are lacking, and the majority of studies conducted to date have concentrated on pharmacokinetic/pharmacodynamic evaluations. Unlike other anti-infective agents, efficacy data in the setting of neonatal candidiasis cannot be extrapolated from adult studies due to differences in the pathophysiology of the disease in this population relative to older children and adults. Data for amphotericin B deoxycholate, fluconazole, and micafungin suggest that these are the current agents of choice for this disease in neonates until data for newer antifungal agents become available. For prophylaxis, data from fluconazole randomized controlled trials will be submitted to the regulatory agencies for labeling. Ultimately, the field of therapeutics for neonatal candidiasis will require multidisciplinary collaboration given the numerous challenges associated with conducting clinical trials in neonates.