What babies need: accelerating access to current and novel antiretroviral drugs in neonates through pharmacokinetic studies

Preventing perinatal HIV acquisition; current gaps and future perspectives

PURPOSE OF REVIEW

Although current treatment could eradicate vertical transmission, in 2022, 130 000 infants acquired HIV globally. HIV suppression with antiretroviral therapy (ART) transforms survival for people living with HIV (PLWH), and prevents transmission, including vertical. International guidelines recommend lifelong ART for PLWH, consequently perinatal HIV acquisition reflects implementation gaps in the HIV care cascade. We summarize these gaps, exploring potential novel approaches and therapeutic innovations towards eliminating vertical HIV transmission.

RECENT FINDINGS

Multifactorial challenges continue to underpin gaps in the HIV care cascade, including accessibility, availability and sustainability of HIV testing, prevention and treatment, alongside stigma, gender-based violence and poverty. Long-acting ART may be important in preventing perinatal HIV acquisition, with early data demonstrating tolerability and efficacy of injectable ART throughout pregnancy, both as HIV treatment and prevention. Carefully selected long-acting broadly neutralizing antibodies (bNAbs) matching circulating, exposing viral envelope sequences have demonstrated safety, clinical trials are ongoing to demonstrate efficacy.

SUMMARY

Emerging clinical studies should prioritize pregnant/lactating people and infants to ensure such therapies are well tolerated and efficacious. Alongside therapeutic innovation, programmatic strategies must address social and economic challenges, ensuring sustainable HIV treatment/prevention programmes and facilitating global elimination of blood-borne viruses.

Advancing Research and Development of Anti-infectives for Children: A Clinical Development Perspective

The HIV treatment landscape for adults has progressed dramatically in recent decades; however, paediatric populations continue to experience delayed and limited access to effective and safe antiretroviral therapy options. Despite current incentive programs, formulation research and development and approved drug dosing for children have been limited, particularly for neonates (aged <4 weeks). Regulatory approval of drug formulations and dosing in children may lag behind adult approvals by years. Formulation and trial design adjustments complicate paediatric drug development, all of which are vital to accommodate for physiological differences, organ maturation, and rapid weight gain, which are most significant in the youngest children. To facilitate more rapid anti-infective drug development for paediatric populations, regulatory agencies provide guidelines that include extrapolating efficacy and safety data from relevant populations; using pharmacokinetic (PK) bridging and modelling to reduce sample sizes and limit the number of PK studies needed before efficacy analyses; and enrolling age- or weight-based cohorts in parallel rather than sequentially for clinical trials. Ensuring access to approved drugs poses an additional challenge, as uncertainty in demand leads to manufacturing and supply complexity with potentially higher costs that can be a barrier to uptake. Here we summarize challenges in drug development for children living with HIV, which are not unique to antiretrovirals. We aim to propose strategies for how model-based approaches and global partnerships can overcome some of these barriers to accelerate paediatric drug development, with particular reference to HIV, and how lessons learnt from HIV could be extended to other anti-infectives.

Twice-Daily Dosing of Dolutegravir in Infants on Rifampicin Treatment: A Pharmacokinetic Substudy of the EMPIRICAL Trial

BACKGROUND

We evaluated dolutegravir pharmacokinetics in infants with human immunodeficiency virus (HIV) receiving dolutegravir twice daily (BID) with rifampicin-based tuberculosis (TB) treatment compared with once daily (OD) without rifampicin.

METHODS

Infants with HIV aged 1-12 months, weighing ≥3 kg, and receiving dolutegravir BID with rifampicin or OD without rifampicin were eligible. Six blood samples were taken over 12 (BID) or 24 hours (OD). Dolutegravir pharmacokinetic parameters, HIV viral load (VL) data, and adverse events (AEs) were reported.

RESULTS

Twenty-seven of 30 enrolled infants had evaluable pharmacokinetic curves. The median (interquartile range) age was 7.1 months (6.1-9.9), weight was 6.3 kg (5.6-7.2), 21 (78%) received rifampicin, and 11 (41%) were female. Geometric mean ratios comparing dolutegravir BID with rifampicin versus OD without rifampicin were area under curve (AUC)0-24h 0.91 (95% confidence interval, .59-1.42), Ctrough 0.95 (0.57-1.59), Cmax 0.87 (0.57-1.33). One infant (5%) receiving rifampicin versus none without rifampicin had dolutegravir Ctrough <0.32 mg/L, and none had Ctrough <0.064 mg/L. The dolutegravir metabolic ratio (dolutegravir-glucuronide AUC/dolutegravir AUC) was 2.3-fold higher in combination with rifampicin versus without rifampicin. Five of 82 reported AEs were possibly related to rifampicin or dolutegravir and resolved without treatment discontinuation. Upon TB treatment completion, HIV viral load was <1000 copies/mL in 76% and 100% of infants and undetectable in 35% and 20% of infants with and without rifampicin, respectively.

CONCLUSIONS

Dolutegravir BID in infants receiving rifampicin resulted in adequate dolutegravir exposure, supporting this treatment approach for infants with HIV-TB coinfection.

Lamivudine and Emtricitabine Dosing Proposal for Children with HIV and Chronic Kidney Disease, Supported by Physiologically Based Pharmacokinetic Modelling

Dose recommendations for lamivudine or emtricitabine in children with HIV and chronic kidney disease (CKD) are absent or not supported by clinical data. Physiologically based pharmacokinetic (PBPK) models have the potential to facilitate dose selection for these drugs in this population. Existing lamivudine and emtricitabine compound models in Simcyp^® (v21) were verified in adult populations with and without CKD and in non-CKD paediatric populations. We developed paediatric CKD population models reflecting subjects with a reduced glomerular filtration and tubular secretion, based on extrapolation from adult CKD population models. These models were verified using ganciclovir as a surrogate compound. Then, lamivudine and emtricitabine dosing strategies were simulated in virtual paediatric CKD populations. The compound and paediatric CKD population models were verified successfully (prediction error within 0.5- to 2-fold). The mean AUC ratios in children (GFR-adjusted dose in CKD population/standard dose in population with normal kidney function) were 1.15 and 1.23 for lamivudine, and 1.20 and 1.30 for emtricitabine, with grade-3- and -4-stage CKD, respectively. With the developed paediatric CKD population PBPK models, GFR-adjusted lamivudine and emtricitabine dosages in children with CKD resulted in adequate drug exposure, supporting paediatric GFR-adjusted dosing. Clinical studies are needed to confirm these findings.

Abacavir safety and effectiveness in young infants with HIV in South African observational cohorts

BACKGROUND

WHO guidelines recommend abacavir in first-line antiretroviral treatment for children and neonates. However, there is no approved dose <3 months of age, and data in neonates are limited.

METHODS

We included infants who initiated ART aged <3 months, between 2006 and 2019, in nine South African cohorts. In those who received abacavir or zidovudine, we described antiretroviral discontinuation rates; and 6- and 12-month viral suppression (<400 copies/mL). We compared infants aged <28 and ≥28 days, those weighing <3 and ≥3 kg.

RESULTS

Overall 837/1643 infants (51%) received abacavir and 443 (27%) received zidovudine. Median (interquartile range, IQR) age was 52 days (23-71), CD4 percentage was 27.9 (19.2-38.0), and weight was 4.0 kg (3.0-4.7) at ART initiation. In those with ≥1 month's follow-up, 100/718 (14%) infants discontinued abacavir, at a median of 17.5 months (IQR 6.5-39.5). Abacavir discontinuations did not differ by age or weight category (p = 0.4 and 0.2, respectively); and were less frequent than zidovudine discontinuations (adjusted hazard ratio 0.14, 95% confidence interval 0.10-0.20). Viral suppression at 12 months occurred in 43/79 (54%) and 130/250 (52%) of those who started abacavir aged <28 and ≥28 days, respectively (p = 0.8); 11/19 (58%) and 31/60 (52%) in those who weighed <3 and ≥3 kg, respectively (p = 0.6); and 174/329 (53%) in those on abacavir versus 77/138 (56%) in those on zidovudine (adjusted odds ratio 1.8, 95% confidence interval 1.0-3.2).

CONCLUSION

Our data suggest that abacavir may be used safely in infants <28 days old or who weigh <3 kg.