For the subjects receiving twice-daily dosing, compared with postpartum, second and third trimester median AUC0–12 were reduced by 26% and median Cmax was reduced by 28% and 29%, respectively, whereas there were no significant differences in Clast. The frequency of subjects meeting the AUC0–12 target for twice-daily dosing was 7/13 (54%) during the second trimester and 19/34 (56%) during the third trimester, compared with 22/27 (81%) postpartum; these differences reached statistical significance only for the third trimester to postpartum comparison. Clast exceeded the DRV EC50 for wild-type HIV of 0.06 μg/mL in all twice-daily subjects except 1 postpartum subject.
No care provider elected to increase the DRV dose for any subject in either arm. Graphs presenting DRV AUC and Clast concentrations for individual subjects across sampling times are depicted in Figure 2. The one-compartment analysis yielded similar DRV exposure parameters to the noncompartmental analysis (data not presented).
Median (interquartile range) ritonavir pharmacokinetic parameters with once-daily dosing during the second trimester, third trimester, and postpartum periods were AUC0–24: 3.7 μg·h·mL−1 (2.5–4.7), 3.7 μg·h·mL−1 (2.3–5.0), 8.2 μg·h·mL−1 (5.8–10.8); Cmax: 0.29 μg/mL (0.22–0.41), 0.27 μg/mL (0.22–0.42), 0.64 μg/mL (0.35–0.90); Clast <0.09 μg/mL (<0.09–0.09), <0.09 μg/mL (<0.09–0.08), 0.09 μg/mL (<0.09–0.14). With twice-daily dosing, median (interquartile range) ritonavir pharmacokinetic parameters during the second trimester, third trimester, and postpartum periods were AUC0–12: 3.9 μg·h·mL−1 (3.1–5.2), 3.8 μg·h·mL−1 (3.1–4.8), 5.6 μg·h·mL−1 (3.7–11.3); Cmax: 0.47 μg/mL (0.32–0.64), 0.46 μg/mL (0.36–0.67), 0.63 μg/mL (0.438–1.08); Clast: 0.16 μg/mL (0.14–0.24), 0.18 μg/mL (0.11–0.25), 0.20 μg/mL (0.12–0.35).
Maternal plasma samples at delivery and umbilical cord blood samples were collected from 43 subjects. DRV concentration was below the assay limit of quantitation in 11 maternal and 15 cord blood samples. When maternal plasma DRV concentration at delivery was above the limit of quantitation, the median (range) DRV cord blood concentration was 0.41 μg/mL (range: <0.09–1.55 μg/mL), maternal plasma delivery concentration was 1.98 μg/mL (range: 0.19–5.62 μg/mL), ratio of cord blood to maternal delivery concentration was 0.18 (range: 0–0.82), and the median time between administration of the last antenatal DRV dose and delivery was 15.1 hour (range: 2.2–43.9 hours). Figure 3 presents the cord blood and maternal delivery DRV concentrations plotted against the time between maternal dosing and delivery.
Overall, DRV was well tolerated during pregnancy and postpartum. No subjects indicated side effects of DRV as a reason for discontinuation. There was 1 toxicity thought by a care provider to be related to study treatment, life-threatening grade 4 anemia in 1 subject, although the study team thought it most likely due to concomitant nucleoside reverse transcriptase inhibitor use. Six subjects had toxicities thought to be possibly related to DRV treatment, including 3 with grade 2 liver function test elevations, 1 with intrauterine growth restriction, 1 with grade 2 hypercholesterolemia, and 1 with gestational diabetes.
Study infants were delivered at a median of 38.6 weeks of gestation (range: 31.6–42.4 weeks) with a median birth weight of 3022 g (range: 1800–4560 g) and a median length of 49 cm (range: 41–54.6 cm). Congenital anomalies were reported in 9 infants: 2 cases of postaxial polydactyly (supernumerary digit), and 1 case each of congenital cystic adenomatoid malformation (congenital pulmonary airway malformation), cardiac murmur, patent foramen ovale, patent ductus arteriosus with the right ventricular hypertrophy, genitourinary chordee, atrial septal defect, ventricular septal defect, and a hearing impairment. With the exception of the cardiac murmur and the patent foramen ovale, which were thought to be possibly related, these were deemed not related to DRV exposure by the clinical care providers and by the study team.
No infant HIV infection data are available for 3 infants whose mothers withdrew from the study shortly after delivery. Of the remaining 63 infants, 1 was HIV infected. This infant had an initial positive HIV RNA on day 3 of life, subsequently confirmed with a second test, and also had congenital toxoplasmosis. The infant was born with weight appropriate for gestational age at 38-week gestation to a mother on the twice-daily arm who enrolled in the third trimester and had an HIV RNA of 66,142 copies per milliliter at delivery. Her predose DRV concentration on the day of her third trimester pharmacokinetic assessment was below the assay limit of detection, suggesting poor adherence. Fifty-eight infants were confirmed uninfected and 4 had negative tests through age 2–9 weeks with no further testing available.
DRV is an HIV protease inhibitor recommended for use as a first-line agent in combination with ritonavir dosed once daily for the treatment of ARV-naive HIV-infected adults and dosed twice daily for the treatment of ARV-experienced adults with at least 1 DRV resistance mutation.22 The physiological changes associated with pregnancy have been shown to decrease drug exposure of other HIV protease inhibitors by 28%–41% compared with postpartum.4–9 Our study is the first to describe DRV pharmacokinetics in a large group of pregnant women receiving both once- and twice-daily administration. Among our subjects, median DRV AUC in the second and third trimesters decreased 38%–39% with once-daily dosing and 26% with twice-daily dosing compared with postpartum. These results are consistent with previously published case reports and smaller series of patients.10–16 Zorrilla et al15 reported a decrease of 17%–24% in DRV AUC in 14 women dosed twice daily in the second and third trimesters. Colbers et al16 reported a mean decrease in DRV AUC of 34% in 6 women with twice-daily dosing and 22% in 18 women with once-daily dosing in the third trimester. Our data are also consistent with a recent presentation describing DRV exposure in pregnant women. Courbon et al described DRV trough concentrations in 33 mostly African women in France receiving once- and twice-daily dosing. Trough DRV concentrations were decreased 20%–25% in the second and third trimesters compared with the first trimester and were lower with once-daily dosing than with twice-daily dosing.23
Although trough concentration is considered the pharmacokinetic parameter that correlates best with protease inhibitor efficacy, trough concentration targets have not been established for DRV.24 The DRV EC50 of wild type HIV is 0.06 μg/mL, below the lower limit of sensitivity of 0.09 μg/mL of the assay used in this study.24 Resistance of HIV to protease inhibitors develops with accumulation of multiple mutations in the HIV genome, so that trough concentrations effective in treatment-naive subjects who lack prior exposure to protease inhibitors may not be effective in treatment-experienced subjects with HIV strains that include protease resistance mutations. DRV trough concentrations are lower with once-daily than twice-daily dosing, and once-daily dosing is recommended only for ARV-naive patients and for treatment-experienced patients with no DRV resistance mutations.22 Our once-daily dosing subjects had median trough concentrations during the second and third trimester of 0.99 and 1.17 μg/mL, compared with median troughs of 2.71 μg/mL in the same women postpartum and 2.16–2.28 μg/mL in clinical trials of once-daily DRV in HIV-infected adults.17 Median trough concentrations were less affected by pregnancy in our twice-daily dosing subjects, who had second and third trimester median troughs of 2.12 and 2.22 μg/mL, compared with 2.51 μg/mL postpartum and 3.39–3.58 μg/mL in clinical trials of HIV-infected adults receiving twice-daily DRV.17
It is difficult to determine the clinical significance of a reduction in DRV exposure of the magnitude we observed and whether HIV-infected pregnant women would benefit from use of an increased dose during pregnancy. In our study, HIV RNA at delivery was below 400 copies per milliliter in 90% of once-daily dosing subjects and 81% of twice-daily dosing subjects. In the study by Zorrilla et al,15 3 of 14 subjects had detectable HIV RNA (>50 copies per milliliter) during pregnancy and 2 of these subjects became undetectable during postpartum follow-up while continuing on DRV. In the study by Colbers et al25 of pregnant women receiving once-daily dosing, 73% had an HIV RNA below 50 copies per milliliter and 93% below 1000 copies per milliliter approaching delivery. There were no infected infants born to the 12 mothers in the Zorrilla et al15 study who remained on therapy at delivery or the 15 mothers in the Colbers et al25 study. In our study, 1 infant was infected out of 63 with at least some virologic testing results available.
The impact of ARV use during pregnancy on the durability of maternal ARV treatment continuing after delivery should also be considered in determining ARV doses during pregnancy. It is unknown whether a sustained period of decreased DRV exposure during pregnancy could result in a more rapid development of resistant virus and treatment failure during long-term postnatal treatment.
Protease inhibitors are highly protein-bound drugs, and plasma protein binding of drugs generally decreases during pregnancy because of decreases in the quantity of albumin and α-1-acid glycoprotein.26 As a result, concentration of free (unbound) drug tends to be higher in pregnant women compared with nonpregnant women with the same total drug concentration. Because free drug is the pharmacologically active fraction of drug in plasma, reductions in protein binding during pregnancy have the potential to at least partially compensate for the reduction in total plasma protease inhibitor concentrations, as has been shown for lopinavir.27–29 Interpretation of the lopinavir protein-binding data has been controversial, with some authors concluding that the protein-binding changes negate the impact of differences in total lopinavir concentration during pregnancy, while others disagree.27–30 Concentrations of free DRV during pregnancy have been reported in 2 studies. Zorrilla et al15 reported free DRV concentrations in 6 second trimester, 7 third trimester, and 11 postpartum subjects. Although total AUC was significantly decreased during pregnancy, there were no significant differences in free DRV AUC or Cmin, or in DRV-free fraction. Colbers et al16 reported no difference in mean (95% confidence interval) DRV-free fraction in 19 women during pregnancy compared with 14 women postpartum [12% (95% CI: 11% to 14%) in the third trimester and 10% (95% CI: 7% to 13%) postpartum]. These studies are too small and lack sufficient clinical correlations to allow definitive conclusions as to whether changes in protein binding during pregnancy may mitigate the decreases in total plasma DRV concentrations. However, the free fraction of DRV is much greater than that of lopinavir, which has a free fraction in nonpregnant adults of 1%–2%, suggesting that changes in protein binding associated with pregnancy are more likely to have a significant impact on free drug concentration of lopinavir than of DRV.31
The magnitude of the reduction in DRV exposure associated with pregnancy that we observed is consistent with the decreases that have been observed for other protease inhibitors.5–9 For some of these drugs, including lopinavir, atazanavir, and nelfinavir, use of increased doses in pregnancy has been shown to result in plasma concentrations equivalent to those seen in nonpregnant adults receiving standard dosing.32–34 Two randomized studies of standard versus increased dose lopinavir in pregnancy suggest that increased lopinavir doses may be beneficial for pregnant women with a detectable viral load at initiation of treatment in pregnancy or with detectable lopinavir resistance mutations.35,36 The package insert for atazanavir, the only protease inhibitor approved in the United States for use in pregnancy, includes a recommendation for an increased dose for treatment-experienced pregnant women in the second or third trimester who are also receiving tenofovir or an H2-receptor antagonist, which have been shown to reduce atazanavir exposure.37 There are no data on DRV pharmacokinetics or clinical outcomes with the use of an increased dose in pregnancy, and an increased twice-daily DRV dose (800 mg or 900 mg DRV with 100 mg ritonavir) is currently under study in another arm of P1026s. Ritonavir exposure was reduced during pregnancy in our subjects, consistent with the reduction seen in other pregnancy studies of ritonavir-boosted protease inhibitors in pregnant women.15,32,33 Although it is not known if use of an increased ritonavir dose would increase DRV exposure during pregnancy, the poor tolerability of ritonavir makes increasing the ritonavir dose unattractive to pregnant women and their care providers.
DRV was well tolerated in our subjects, who demonstrated little toxicity attributed to DRV use. Placental transfer of DRV was poor, as has been demonstrated for other protease inhibitors.38 The median ratio of maternal to cord blood DRV was 0.18, consistent with that seen in previous studies, and this ratio reached a steady state at around 8 hours after administration of the last maternal dose before delivery.15,25
There are several limitations to our study. Our study used an opportunistic design, enrolling pregnant women receiving DRV as part of clinical care, and enrolled a very heterogeneous population. Women enrolled at various stages of pregnancy and with varying past histories of ARV use, ranging from none to years of treatment with multiple regimens. Their duration of DRV treatment at the time of third trimester sampling ranged from 2 weeks to nearly 5 years. Our study population was biased toward those who tolerated and responded well to DRV therapy, as pregnant women with early DRV toxicity or lack of efficacy may have been switched to other ARVs and would not have been eligible for enrollment. Clinical care providers determined whether subjects received once- or twice-daily dosing and were responsible for making adjustments to the ARV regimens because of drug toxicity and therapeutic response. Our study included no rigorous measure of adherence, although inspection of the intensive pharmacokinetic profiles did reveal whether subjects were at steady state at the time of sampling. In addition, we measured concentrations of total but not free DRV, so we can provide no new data to address the question of the impact of protein-binding changes on free DRV concentrations during pregnancy.
In summary, our study of a large number of women demonstrates a significant reduction in DRV plasma concentrations during pregnancy with once- and twice-daily dosing, consistent with reductions seen with other proteases inhibitors during pregnancy. Given the absence of established DRV trough concentration targets, it is reasonable to use typical plasma concentrations seen in nonpregnant adults as a therapeutic target when DRV is used during pregnancy. To achieve DRV plasma concentrations during pregnancy equivalent to those seen in nonpregnant adults, an increased twice-daily dose may be necessary. This may be especially important for treatment-experienced women who may have developed ARV resistance mutations.
The authors thank the study participants and their families. In addition to the authors, members of the IMPAACT P1026s protocol team include Francesca Aweeka, Michael Basar, Emily Barr, Mark Byroads, Nantasak Chotivanich, Lisa M. Frenkel, Kathy George, Elizabeth Hawkins, Kathleen Adriane Hernandez, Amy Jennings, Rita Patel, and Pra-ornsuda Sukrakanchana. The authors also thank the following investigators and staff at the enrolling sites: New Jersey Medical School CRS (Linda Bettica, RN; Charmane Calilap-Bernardo, MA, PNPC; Arlene Bardeguez, MD, MPH); Texas Children's Hospital CRS (Shelley Buschur, RN, CNM; Chivon Jackson, RN, BSN, ADN; Mary Paul, MD); Columbia CRS (Philip La Russa, MD); University of Miami Pediatric Perinatal HIV/AIDS CRS (Claudia Florez, MD; Patricia Bryan, BSN, MPH; Monica Stone, MD); University of California San Diego Mother-Child-Adolescent Program CRS [Andrew D. Hull, MD; Caffery, RN, MSN; Stephen A. Spector, MD]; Duke University Medical Center CRS (Joan Wilson, RN, BSN, MPH; Julieta Giner, RN, ACRN; Margaret A. Donnelly, PA-C); New York University, New York NICHD CRS (Nagamah Deygoo, MD; Aditya Kaul, MD; William Borkowsky, MD); Jacobi Medical Center Bronx NICHD CRS (Mindy Katz, MD; Raphaelle Auguste, RN; Andrew Wiznia, MD); University of South Florida—Tampa NICHD CRS (Karen L. Bruder, MD; Gail Lewis, RN; Denise Casey, RN); University of Southern California School of Medicine—Los Angeles County NICHD CRS (Françoise Kamer, MD; LaShonda Spencer, MD; James Homans, MD); University of Colorado Denver NICHD CRS (Torri Metz, MD; Jenna Wallace, MSW; Alisa Katai, MHA); Hospital dos Servidores Rio de Janeiro NICHD CRS (Esau C. Joao, MD, PhD; Plinio Tostes Berardo Carneiro da Cunha, MD, PhD; Maria Isabel Fragoso da Silveira Gouvêa, MD); Hospital General de Agudos Buenos Aires NICHD CRS (Marcelo H. Losso, MD; Silvina A. Ivalo, MD; Alejandro Hakim, MD); Miller Children's Hospital NICHD CRS (Audra Deveikis, MD; Jagmohan Batra, MD; Janielle Jackson Alvarez, RN); Hospital Santa Casa Porto Alegre Brazil NICHD CRS (Regis Kreitchmann, PhD, MD; Debora Fernandes Coelho, MN, PhD; Marcelo Comerlato Scotta, MSc, MD); St Jude CRS (Katherine M. Knapp, MD; Nina Sublette, FNP, PhD; Thomas Wride, MS); University of Puerto Rico Pediatric HIV/AIDS Research Program CRS (Irma L. Febo, MD; Ruth Santos, RN, MPH; Vivian Tamayo, MD); The Children's Hospital of Philadelphia (Steven D. Douglas, MD; Carol A. Vincent, PhD, CRNP; Samuel Parry, MD); Bronx-Lebanon Hospital CRS (Jenny Gutierrez, MD; Mary Elizabeth Vachon, MPH; Murli Purswani, MD); Siriraj Hospital Mahidol University, Bangkok, Thailand CRS (Thanomsak Anekthananon, MD; Amphan Chalermchokcharoenkit, MD; Kulkanya Chokephaibulkit, MD).
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Keywords:Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
darunavir; pregnancy; HIV; pharmacokinetics