Pregnancy Exposure Registry
There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiretrovirals during pregnancy. This registry does not include Trogarzo, but likely includes patients’ concomitant antiretroviral drugs. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1–800–258–4263.
Risk Summary
Based on animal data, ibalizumab-uiyk use during pregnancy may cause reversible immunosuppression (CD4+ T cell and B cell lymphocytopenia) in infants exposed to ibalizumab-uiyk in utero. Immunoglobulin G (IgG) antibodies, such as ibalizumab-uiyk, are transported across the placenta in significant amounts, especially near term; therefore, ibalizumab-uiyk has the potential to be transferred from the mother to the developing fetus (see Clinical Considerations). There are no available data on ibalizumab-uiyk use in pregnant women to evaluate for a drug- associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes. The background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.
In a reproductive study in monkeys, reversible decreases in CD4+ T cells and B cells and increases in CD8+ T cells were observed within the first 4 weeks after birth in infants born to pregnant monkeys receiving ibalizumab-uiyk intravenously (see Data). Lymphocyte counts returned to near normal levels by 3 months of age. One infant monkey died from a systemic viral infection that may be related to ibalizumab-uiyk-induced immunosuppression. No malformations or premature births were observed in this study.
Clinical Considerations
Fetal/Neonatal Adverse Reactions
Immunoglobulin G (IgG) antibodies are increasingly transported across the placenta as pregnancy progresses, with the largest amount transferred during the third trimester. Administration of TROGARZO during pregnancy may affect immune responses in the in utero-exposed infant. For infants with perinatal exposure to TROGARZO, immune phenotyping of the peripheral blood, including CD4+ T cell and B cell counts, is recommended. Expert consultation is also recommended to provide guidance on monitoring and management (e.g., need for antibiotic or immunoprophylaxis) of exposed infants based on the degree of immunosuppression observed. The safety of administering live or live-attenuated vaccines in exposed infants is unknown.
Data
Animal Data
In an enhanced pre- and post-natal development (ePPND) study, pregnant cynomolgus monkeys were administered intravenous doses of either vehicle or 110 mg/kg ibalizumab-uiyk every week from Gestation Day 20-22 (GD 20-22) until parturition on GD 160 ± 10. Significant changes in infant monkey immune cell levels on Postnatal Day (PND) 14 (mean decreases of 78% in CD4+ T cells and 46% in B cells and increases of 2.3-fold in CD8+ T cells) and PND 28 (mean decreases of 73% in CD4+ T cells and increases of 2.2-fold in CD8+ T cells), attributed to in utero ibalizumab-uiyk exposure, were observed relative to concurrent controls. The lymphocyte changes correlated with infant ibalizumab-uiyk serum concentrations and appeared to return to near normal levels between PND 28-91, when ibalizumab-uiyk concentrations were nearly undetectable. Although ibalizumab-uiyk exposure in these infant monkeys may be significantly higher than in human infants following in utero exposure at the recommended human maintenance dose, the risk of ibalizumab-uiyk-induced immunosuppression in human infants is possible. No meaningful differences in infant monkey lymphocyte counts were observed on PND 180. Further, no differences in immune cell function were observed in a T cell-dependent response assay conducted on PND 138 to 180 ± 2 following immunization of the infant monkeys with keyhole limpet hemocyanin. One treatment-group infant monkey died on PND 24 from a systemic viral infection with secondary superficial bacterial infection which was acquired during the postnatal period. Despite the low incidence (1 of 20 infants), the death may be related to ibalizumab-uiyk-induced immunosuppression. Decreases in CD4+ T cells (93%), and B cells (92%) were observed in this infant on PND 14, and decreased cellularity was observed in the spleen, thymus and mandibular lymph node. Unlike the rest of the ibalizumab-exposed infant monkey population, this infant also exhibited a decrease in CD8+ T cells of 71% on PND 14. Body weight was also decreased in this infant between PND 14 and 24. No structural abnormalities were observed among the ibalizumab-uiyk-exposed infants. In addition, no maternal toxicities, including no changes in maternal lymphocyte subsets or effects on embryo-fetal survival, were observed.
Risk Summary
The Centers for Disease Control and Prevention recommend that HIV-1-infected mothers in the United States not breastfeed their infants to avoid the risk of postnatal transmission of HIV-1 infection.
No data are available regarding the presence of TROGARZO in human milk, the effects on the breastfed child, or the effects on milk production. Human IgG is present in human milk, although published data indicate that antibodies in breast milk do not enter the neonatal or infant circulation system in substantial amounts. Because of the potential for HIV-1 transmission, instruct mothers not to breastfeed if they are receiving TROGARZO.
Mechanism of Action
Ibalizumab-uiyk, a recombinant humanized monoclonal antibody, blocks HIV-1 from infecting CD4+ T cells by binding to domain 2 of CD4 and interfering with post-attachment steps required for the entry of HIV-1 virus particles into host cells and preventing the viral transmission that occurs via cell-cell fusion.
Ibalizumab-uiyk Does Not Impact CD4 Function
The binding specificity of ibalizumab-uiyk to domain 2 of CD4 allows ibalizumab-uiyk to block viral entry into host cells without causing immunosuppression. Epitope mapping studies indicate that ibalizumab-uiyk binds to a conformational epitope located primarily in domain 2 of the extracellular portion of the CD4 receptor. This epitope is positioned on the surface of CD4 opposite to the site in domain 1 that is required for CD4 binding of the MHC class II molecules and therefore does not interfere with CD4-mediated immune functions. Additionally, ibalizumab-uiyk does not interfere with gp120 attachment to CD4.
Antiviral Activity
Ibalizumab-uiyk inhibits the replication of CCR5- and CXCR4-tropic laboratory strains and primary isolates of HIV-1 in phytohemagglutinin stimulated peripheral blood lymphocytes. The median EC50 value (50% effective concentration) for ibalizumab-uiyk against HIV-1 group M isolates (subtypes A, B, C, D, E, or O) was 8 ng/mL (n = 15, range of 0.4 to 600 ng/mL) in cell culture, with lower susceptibility observed in macrophage-tropic HIV-1 strains (BaL, JR-CSF, YU2, and ADA-M). In a single-cycle infection assay, ibalizumab-uiyk inhibited 17 clinical isolates of subtype B with a median EC50 value of 12 ng/mL (range of 8.8 to 16.9 ng/mL; mean 12 ± 3 ng/mL) and a median maximum percentage inhibition (MPI) of 97% (range of 89 to 99%; mean 97 ± 3%). Three CCR5-tropic clinical isolates from subtypes B, C, and D, were inhibited with EC50 values ranging from 59-66 ng/mL and 3 CXCR4-tropic clinical isolates from subtypes B, C, and D, with EC50 values ranging from 44-59 ng/mL.
Antiviral Activity in Combination with Other Antiviral Agents
No antagonism was observed when PBMCs or MAGI-CCR5 cells infected with the subtype B Ba-L or ADA variants of HIV-1 were incubated with ibalizumab-uiyk in combination with the CCR5 co-receptor antagonist maraviroc or when PBMCs infected with the subtype B HT/92/599 variant of HIV-1 were incubated with ibalizumab-uiyk in combination with the gp41 fusion inhibitor enfuvirtide; a nonnucleoside reverse transcriptase inhibitor (efavirenz); nucleoside analog reverse transcriptase inhibitors (abacavir, didanosine, emtricitabine, tenofovir, or zidovudine); or a protease inhibitor (atazanavir).
Antiviral Activity in Antiretroviral-Resistant Virus
Subjects enrolled in TMB-301 were heavily treatment-experienced subjects infected with multidrug resistant HIV-1. Ibalizumab-uiyk inhibited 38 baseline isolates at a median EC50 value of 31 ng/mL (range of 13 to 212 ng/mL; mean 39 ± 35 ng/mL) with a median MPI of 97% (range of 41-100%; mean 91 ± 14%). For 10 subjects in TMB-301 who failed treatment, at the time of failure the median ibalizumab-uiyk EC50 value was 566 ng/mL (range of 148 to >54,900 ng/mL; mean 11,768 ± 21,650 ng/mL) representing an EC50 value shift of >18-fold. For the HIV-1 derived from the same subjects, the median MPI was 55% (range of 43-72%; mean 56 ± 8%) representing a 42 percentage point reduction.
Decreased Susceptibility
Decreased susceptibility to ibalizumab-uiyk, as defined by a decrease in MPI, has been observed in some subjects experiencing virologic failure and may be associated with genotypic changes in the HIV-1 envelope coding sequence that results in the loss of potential N-linked glycosylation sites (PNGS) in the V5 loop of gp120. The clinical significance of decreased susceptibility to ibalizumab-uiyk has not been established.
Cross-Resistance
Phenotypic and genotypic test results revealed no evidence of cross-resistance between ibalizumab-uiyk and any of the approved classes of anti-retroviral drugs (CCR5 co-receptor antagonists, gp41 fusion inhibitors, integrase strand transfer inhibitors [INSTIs], non-nucleos(t)ide reverse transcriptase inhibitors [NNRTIs], nucleos(t)ide reverse transcriptase inhibitors [NRTIs], or protease inhibitors [PIs]). Ibalizumab-uiyk is active against HIV-1 resistant to all approved antiretroviral agents and exhibits antiretroviral activity against R5-tropic, X4-tropic, and dual-tropic HIV-1.
Decreased susceptibility to ibalizumab-uiyk following multiple dose administrations of ibalizumab-uiyk has been observed in some subjects. Cell culture studies performed with HIV-1 variants with reduced susceptibility to ibalizumab-uiyk indicate that phenotypic changes associated with resistance to ibalizumab-uiyk do not alter susceptibility to other approved agents and do not result in the selection of CD4-independent viral isolates.
CD4 Polymorphisms and Ibalizumab-uiyk Activity
CD4 polymorphisms reported in public databases were analyzed to determine if any naturally occurring amino acid substitutions in the CD4 molecule from different human populations would potentially impact the antiviral activity of ibalizumab-uiyk. None of the known CD4 polymorphisms are likely to have an impact on ibalizumab-uiyk binding to CD4.
Trial TMB-301:
Trial TMB-301 was a single arm, multicenter clinical trial conducted in 40 heavily treatment-experienced HIV-infected subjects with multidrug resistant HIV-1. Subjects were required to have a viral load greater than 1,000 copies/mL and documented resistance to at least one antiretroviral medication from each of three classes of antiretroviral medications as measured by resistance testing. Subjects must have been treated with antiretrovirals for at least 6 months and be failing or had recently failed (i.e., in the last 8 weeks) therapy.
The trial was composed of three discrete periods:
- Control period (Day 0 to Day 6): Subjects were either monitored on their current failing therapy or received no therapy if they had failed and discontinued treatment within the 8 weeks preceding screening. This was an observational period to establish baseline HIV viral load.
- Functional monotherapy period (Day 7 to Day 13): All subjects received a 2,000 mg loading dose of TROGARZO on Day 7. Subjects on a failing ART regimen continued to receive their failing regimen in addition to the loading dose of TROGARZO. This period was to establish the virologic activity of TROGARZO.
- Maintenance period (Day 14 to Week 25): On Day 14 of the treatment period, viral load was assessed for the primary endpoint, and thereafter the background regimen was optimized to include at least one drug to which the subjects virus was susceptible. The use of an investigational drug(s) as a component of the optimized background regimen was allowed. Beginning at Day 21, an 800 mg maintenance dose of TROGARZO was administered every two weeks through Week 25. This period was to establish the safety and durability of virologic suppression of TROGARZO when used in combination with an optimized background regimen.
The majority of subjects in Trial TMB-301 were male (85%), white (55%) and between 23 and 65 years of age (mean [SD] age: 50.5 [11.0] years). At Baseline, median viral load and CD4+ T cell counts were 35,350 copies/mL and 73 cells/mm3, respectively. The subjects were heavily treatment-experienced: 53% of participants had been treated with 10 or more antiretroviral drugs prior to trial enrollment; 98% percent had been treated with NRTIs, 98% with PIs, 80% with NNRTIs, 78% with INSTIs, 30% with gp41 fusion inhibitors, and 20% with CCR5 co-receptor antagonists.
The primary efficacy endpoint was the proportion of subjects achieving a 0.5 log10 decrease in viral load from the beginning to the end of the "Functional monotherapy period" as compared to the proportion of subjects achieving a 0.5 log10 decrease from the beginning to the end of the "Control period", as defined above. The results of the primary endpoint analysis are shown in Table 5 below.
Table 5. Proportion of Subjects Achieving a 0.5 log10 Decrease in Viral Load at the End of the Control and Functional Monotherapy Periods | Proportion of Subjects Achieving a 0.5 log10 Decrease in Viral Load N=40 | 95% CI exact 95% confidence interval. p < 0.0001 based on McNemars test comparing the proportion of subjects achieving 0.5 log10 decrease in viral load at the end of the control and functional monotherapy periods. |
| End of Control Period | 3% | (0.06%, 13%) |
| End of Functional Monotherapy Period | 83% | (67%, 93%) |
At Week 25, viral load <50 and <200 HIV-1 RNA copies/mL was achieved in 43% and 50% of subjects, respectively. Fifty-five percent of subjects had a 1 log10 reduction in viral load, and 48% of subjects had a 2 log10 reduction in viral load at Week 25. An increase in the mean and median number of CD4+ T-cells (44 cells/mm3 and 17 cells/mm3, respectively) was observed from Baseline to Week 25. Week 25 outcomes are shown in Table 6 and Table 7.
Table 6. Trial TMB 301 Virologic Outcomes (Snapshot Algorithm) at Week 25 | TROGARZO (N=40) |
HIV RNA < 50 copies/mL at Week 25 HIV RNA 50 copies/mL at Week 25*included subjects who had ≥ 50 copies/mL in the Week 25 window, subjects who discontinued study drug due to lack of efficacy, and subjects who discontinued study drug for reasons other than an AE, death and at the time of discontinuation had a viral value ≥ 50 copies/mL | 43% 45% |
HIV RNA < 200 copies/mL at Week 25 HIV RNA 200 copies/mL at Week 25included subjects who had ≥ 200 copies/mL in the Week 25 window, subjects who discontinued study drug due to lack of efficacy, and subjects who discontinued study drug for reasons other than an AE, death and at the time of discontinuation had a viral value ≥ 200 copies/mL | 50% 38% |
No virologic data at Week 25 Discontinued due to AE or death | 13% |
Table 7. Virologic Response at Week 25 by Baseline CD4 Cell count, Viral Load, Integrase Inhibitor Resistance and OSS | Subjects achieving <50 HIV-1 RNA copies/mL (%) | Subjects achieving <200 HIV-1 RNA copies/mL (%) |
CD4 Cell Counts <50 (n=17) 50-200 (n=10) >200 (n=13) | 18 60 62 | 24 70 69 |
Viral Load 100,000 (n=33) >100,000 (n=7) | 49 14 | 58 14 |
Resistance With INSTI Resistance (n=27) Without INSTI Resistance (n=13) | 41 46 | 44 62 |
OSS 0 (n=5) 1 (n=12) 2 (n=18) 3 (n=3) 4 (n=2) | 20 42 50 33 50 | 20 50 61 33 50 |
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