Applying the Noninferiority Paradigm to Assess Exposure-Response Similarity and Dose Between Pediatric and Adult Patients

The use of extrapolation of efficacy in pediatric drug development programs is possible when disease progression and treatment response are similar in adult and pediatric populations. Historically, the exposure-response (E-R) similarity was assessed by visual inspection of 2 E-R curves to support pediatric extrapolation. The aim of this study was to develop a quantitative framework to describe the E-R relationship and the difference in E-R between pediatric and adult patients based on accumulated experience in pediatric drug development programs. Using clinical data for 8 drugs with either a linear or nonlinear E-R relationship, we adapted the methodology used in noninferiority testing to assess the E-R similarity between adult and pediatric patients at the targeted drug exposure. We implemented bootstrap-based and Bayesian-based methodologies to estimate the probability of concluding noninferiority of the E-R relationship. This approach provides objective criteria that can be applied to an assessment of E-R noninferiority in 2 populations to support extrapolation of efficacy in drug development programs from adults to pediatric populations.

Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial

IMPORTANCE

A prior pilot study demonstrated the systemic absorption of 4 sunscreen active ingredients; additional studies are needed to determine the systemic absorption of additional active ingredients and how quickly systemic exposure exceeds 0.5 ng/mL as recommended by the US Food and Drug Administration (FDA).

OBJECTIVE

To assess the systemic absorption and pharmacokinetics of the 6 active ingredients (avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate) in 4 sunscreen products under single- and maximal-use conditions.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial at a clinical pharmacology unit (West Bend, Wisconsin) was conducted in 48 healthy participants. The study was conducted between January and February 2019.

INTERVENTIONS

Participants were randomized to 1 of 4 sunscreen products, formulated as lotion (n = 12), aerosol spray (n = 12), nonaerosol spray (n = 12), and pump spray (n = 12). Sunscreen product was applied at 2 mg/cm2 to 75% of body surface area at 0 hours on day 1 and 4 times on day 2 through day 4 at 2-hour intervals, and 34 blood samples were collected over 21 days from each participant.

MAIN OUTCOMES AND MEASURES

The primary outcome was the maximum plasma concentration of avobenzone over days 1 through 21. Secondary outcomes were the maximum plasma concentrations of oxybenzone, octocrylene, homosalate, octisalate, and octinoxate over days 1 through 21.

RESULTS

Among 48 randomized participants (mean [SD] age, 38.7 [13.2] years; 24 women [50%]; 23 white [48%], 23 African American [48%], 1 Asian [2%], and 1 of unknown race/ethnicity [2%]), 44 (92%) completed the trial. Geometric mean maximum plasma concentrations of all 6 active ingredients were greater than 0.5 ng/mL, and this threshold was surpassed on day 1 after a single application for all active ingredients. For avobenzone, the overall maximum plasma concentrations were 7.1 ng/mL (coefficient of variation [CV], 73.9%) for lotion, 3.5 ng/mL (CV, 70.9%) for aerosol spray, 3.5 ng/mL (CV, 73.0%) for nonaerosol spray, and 3.3 ng/mL (CV, 47.8%) for pump spray. For oxybenzone, the concentrations were 258.1 ng/mL (CV, 53.0%) for lotion and 180.1 ng/mL (CV, 57.3%) for aerosol spray. For octocrylene, the concentrations were 7.8 ng/mL (CV, 87.1%) for lotion, 6.6 ng/mL (CV, 78.1%) for aerosol spray, and 6.6 ng/mL (CV, 103.9%) for nonaerosol spray. For homosalate, concentrations were 23.1 ng/mL (CV, 68.0%) for aerosol spray, 17.9 ng/mL (CV, 61.7%) for nonaerosol spray, and 13.9 ng/mL (CV, 70.2%) for pump spray. For octisalate, concentrations were 5.1 ng/mL (CV, 81.6%) for aerosol spray, 5.8 ng/mL (CV, 77.4%) for nonaerosol spray, and 4.6 ng/mL (CV, 97.6%) for pump spray. For octinoxate, concentrations were 7.9 ng/mL (CV, 86.5%) for nonaerosol spray and 5.2 ng/mL (CV, 68.2%) for pump spray. The most common adverse event was rash, which developed in 14 participants.

CONCLUSIONS AND RELEVANCE

In this study conducted in a clinical pharmacology unit and examining sunscreen application among healthy participants, all 6 of the tested active ingredients administered in 4 different sunscreen formulations were systemically absorbed and had plasma concentrations that surpassed the FDA threshold for potentially waiving some of the additional safety studies for sunscreens. These findings do not indicate that individuals should refrain from the use of sunscreen.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03582215.

Effect of Sunscreen Application Under Maximal Use Conditions on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial

IMPORTANCE

The US Food and Drug Administration (FDA) has provided guidance that sunscreen active ingredients with systemic absorption greater than 0.5 ng/mL or with safety concerns should undergo nonclinical toxicology assessment including systemic carcinogenicity and additional developmental and reproductive studies.

OBJECTIVE

To determine whether the active ingredients (avobenzone, oxybenzone, octocrylene, and ecamsule) of 4 commercially available sunscreens are absorbed into systemic circulation.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial conducted at a phase 1 clinical pharmacology unit in the United States and enrolling 24 healthy volunteers. Enrollment started in July 2018 and ended in August 2018.

INTERVENTIONS

Participants were randomized to 1 of 4 sunscreens: spray 1 (n = 6 participants), spray 2 (n = 6), a lotion (n = 6), and a cream (n = 6). Two milligrams of sunscreen per 1 cm2 was applied to 75% of body surface area 4 times per day for 4 days, and 30 blood samples were collected over 7 days from each participant.

MAIN OUTCOMES AND MEASURES

The primary outcome was the maximum plasma concentration of avobenzone. Secondary outcomes were the maximum plasma concentrations of oxybenzone, octocrylene, and ecamsule.

RESULTS

Among 24 participants randomized (mean age, 35.5 [SD, 1.5] years; 12 (50%] women; 14 [58%] black or African American; 14 [58%]), 23 (96%) completed the trial. For avobenzone, geometric mean maximum plasma concentrations were 4.0 ng/mL (coefficient of variation, 6.9%) for spray 1; 3.4 ng/mL (coefficient of variation, 77.3%) for spray 2; 4.3 ng/mL (coefficient of variation, 46.1%) for lotion; and 1.8 ng/mL (coefficient of variation, 32.1%). For oxybenzone, the corresponding values were 209.6 ng/mL (66.8%) for spray 1, 194.9 ng/mL (52.4%) for spray 2, and 169.3 ng/mL (44.5%) for lotion; for octocrylene, 2.9 ng/mL (102%) for spray 1, 7.8 ng/mL (113.3%) for spray 2, 5.7 ng/mL (66.3%) for lotion, and 5.7 ng/mL (47.1%) for cream; and for ecamsule, 1.5 ng/mL (166.1%) for cream. Systemic concentrations greater than 0.5 ng/mL were reached for all 4 products after 4 applications on day 1. The most common adverse event was rash, which developed in 1 participant with each sunscreen.

CONCLUSIONS AND RELEVANCE

In this preliminary study involving healthy volunteers, application of 4 commercially available sunscreens under maximal use conditions resulted in plasma concentrations that exceeded the threshold established by the FDA for potentially waiving some nonclinical toxicology studies for sunscreens. The systemic absorption of sunscreen ingredients supports the need for further studies to determine the clinical significance of these findings. These results do not indicate that individuals should refrain from the use of sunscreen.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03582215.

Effect of amniotic fluid on platelet thromboxane production

We have studied the effect of amniotic fluid on thromboxane A2 (TXA2) production as an initial step in an evaluation of the role of this metabolite as the mediator of the pulmonary hypertension that accompanies perinatal aspiration. Term amniotic fluid enhanced platelet thromboxane B2 (TXB2) production in the presence of the aggregating agents thrombin and arachidonic acid, activity being confined to the lipid fraction. Compared with a baseline production of 1.4 +/- 0.45 pmol TXB2/10(6) platelets in response to thrombin (1 U/ml), unfractionated amniotic fluid or its lipid fraction enhanced TXB2 production to 2.87 +/- 0.53 and 2.81 +/- 0.62 pmol, respectively (P less than 0.01). Values for the aqueous extract were no different from buffer control values (1.14 +/- 0.5). No enhancement of platelet TXB2 production was observed in amniotic fluid obtained at 15 to 17 weeks. Similar activity was observed with either adult or neonatal platelets. This thromboxane enhancing property of amniotic fluid appears to be distinct from its thrombin generating property. Following perinatal aspiration, in situ production of thrombin and proaggregatory TXA2 could recruit more platelets, enhance local TXA2 production, and be responsible for the platelet thrombi that have been documented at autopsy in the pulmonary microcirculation in infants with perinatal aspiration syndrome.

Effect of changes in oxygen tension on vascular and platelet hydroxyacid metabolites. II. Hypoxia increases 15-hydroxyeicosatetraenoic acid, a proangiogenic metabolite

Current strict O2 management may be precipitating more severe retinopathy of prematurity than would occur with a more lenient approach. Hypoxemia in an animal model has also been found to worsen retinal neovascularization. It has recently been shown that the hydroxyeicosatetraenoic acids can modulate angiogenesis. 15-Hydroxyeicosatetraenoic acid is proangiogenic, whereas 12-hydroxyeicosatetraenoic acid is an antiangiogenic metabolite. In vitro exposure of paired human neonatal vessels (n = 7) to hypoxia enhanced the production of total vascular hydroxyacids (232 +/- 36 pmol/mg of protein [experimental group] nu 168 +/- 31 pmol [control group]; P less than .01). The increase in vascular 15-hydroxyeicosatetraenoic acid under hypoxic conditions was even more significant (P less than .001). However, platelet production of 12-hydroxyeicosatetraenoic acid was not significantly affected by hypoxia. These observations suggest a possible biochemical basis for the abnormal angiogenic process that occurs during the proliferation phase of the retinopathy of prematurity. The production of local hydroxyeicosatetraenoic acids in tissues manifesting abnormal neovascularization needs to be further evaluated.

Effects of hyperoxia and hypoxia on vascular prostacyclin formation in vitro

Exposure to high oxygen (O2) concentrations, especially in the neonate, is associated with the development of pathologic syndromes characterized by vascular involvement including the retinopathy of prematurity. Some of the initial vascular changes observed appear consistent with a reduction in prostacyclin formation. Exposure of human umbilical arteries to oxygen resulted in more than 30% inhibition in the ability of the vessels to produce prostacyclin either from endogenous stores of arachidonic acid or from exogenously provided substrate. In contrast, hypoxia (which more closely approximates the fetal environment) resulted in more than 30% stimulation in the production of prostacyclin from either endogenous or exogenous arachidonic acid. When microsomes were prepared from treated arterial segments, these effects persisted. In vitro results suggest that neonates exposed to O2 after delivery may experience a marked decrease in vascular prostacyclin formation. Inhibition of the production of this potent vasodilator and antithrombotic metabolite could play an important role in the acute exudative phase of O2 toxicity.

Effects of hydrogen peroxide on vascular arachidonic acid metabolism

Hydrogen peroxide (H2O2) released by granulocytes during phagocytosis has previously been demonstrated to affect the function of other cellular elements including red cells and platelets. We have evaluated the effect of H2O2 on vascular arachidonic acid (AA) metabolism. Exposure of human vascular segments to H2O2 (25 to 200 microM) results in a concentration dependent inhibition in the ability of these vessels to produce PGI2 either from endogenous stores of AA, or from exogenously provided substrate. The inhibition of PGI2 production was present at 5 minutes post addition of H2O2, with maximal inhibitory effect occurring by 15 minutes. Production of 6 Keto PGF1 alpha from exogenously provided 14C AA was similarly inhibited in isolated microsomes from these vessels, as was the production of the other vascular cyclo-oxygenase metabolites PGE2 and PGF2 alpha. These results demonstrate that the major effect of H2O2 on vascular AA metabolism appears to occur at the cyclo-oxygenase level. Vascular inhibition of PGI2 formation caused by the local release of H2O2 from phagocytizing cellular elements may play a role in the pathophysiology of the inflammatory process.