Population Pharmacokinetics of Sacituzumab Govitecan in Patients with Metastatic Triple-Negative Breast Cancer and Other Solid Tumors

BACKGROUND AND OBJECTIVE

Sacituzumab govitecan (SG) is an antibody-drug conjugate composed of an antibody with affinity for Trop-2 coupled to SN-38 via hydrolyzable linker. SG is approved for patients with metastatic triple-negative breast cancer (mTNBC) who have received two or more prior chemotherapies (at least one in a metastatic setting) and for patients with pretreated hormone receptor positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer.

METHODS

In these analyses, the pharmacokinetics of SG, free SN-38, and total antibody (tAB) were characterized using data from 529 patients with mTNBC or other solid tumors across two large clinical trials (NCT01631552; ASCENT, NCT02574455). Three population pharmacokinetic models were constructed using non-linear mixed-effects modeling; clinically relevant covariates were evaluated to assess their impact on exposure. Models for SG and tAB were developed independently whereas free SN-38 was sequentially generated via a first-order release process from SG.

RESULTS

Pharmacokinetics of the three analytes were each described by a two-compartment model with estimated body weight-based scaling exponents for clearance and volume. Typical parameter estimates for clearance and steady-state volume of distribution were 0.133 L/h and 3.68 L for SG and 0.0164 L/h and 4.26 L for tAB, respectively. Mild-to-moderate renal impairment, mild hepatic impairment, age, sex, baseline albumin level, tumor type, UGT1A1 genotype, or Trop-2 expression did not have a clinically relevant impact on exposure for any of the three analytes.

CONCLUSIONS

These analyses support the approved SG dosing regimen of 10 mg/kg as intravenous infusion on days 1 and 8 of 21-day cycles and did not identify a need for dose adjustment based on evaluated covariates or disease characteristics.

Dose Titration of Ixazomib Maintenance Therapy in Transplant-Ineligible Multiple Myeloma: Exposure-Response Analysis of the TOURMALINE-MM4 Study

Ixazomib has been approved in several countries as single agent maintenance therapy in newly diagnosed multiple myeloma (NDMM), in both post-transplant and transplant-ineligible settings, based on two Phase 3 studies. In these maintenance studies, patients were initially administered 3 mg ixazomib, escalating to 4 mg if the initial dose level was well-tolerated through Cycles 1-4. Here, we report the results of exposure-response analyses of TOURMALINE-MM4, wherein relationships between exposure and clinical response, dose adjustments, and selected adverse events (AEs) were evaluated. Similar progression-free survival (PFS) benefits were observed across the range of ixazomib exposures achieved in the study. Moreover, increased ixazomib exposures corresponded to a higher probability of maintaining complete response (CR). Exposure was not a significant predictor (p>0.05) of hematological adverse events (anemia, neutropenia, thrombocytopenia) and peripheral neuropathy; however, higher exposures did correlate to increased probabilities of experiencing diarrhea, vomiting, nausea, rash, and fatigue. While ixazomib exposure was not predictive of dose reductions, lower apparent clearance values (corresponding to higher systemic exposures) were correlated with a reduced likelihood of escalating to the 4 mg dose. Thus, the dose titration approach balanced patient benefit and risk; it ensured that only patients for whom the 3 mg dose was safe/tolerable escalated to the higher dose, while maximizing the fraction of patients (85%) who were able to derive additional clinical benefit at 4 mg. Collectively, these results highlight the value of safety-driven personalized dosing to maximize patient benefit/risk.

Characterization and management of adverse events observed with mobocertinib (TAK-788) treatment for EGFR exon 20 insertion-positive non-small cell lung cancer

BACKGROUND

Mobocertinib has demonstrated durable clinical benefit in platinum-pretreated patients (PPP) with epidermal growth factor receptor exon 20 insertion-positive non-small cell lung cancer (NSCLC).

RESEARCH DESIGN AND METHODS

Pooled safety analysis of two studies included patients with NSCLC (N = 257) treated with the recommended phase 2 dose (RP2D) of mobocertinib (160 mg once daily). We report overall safety (treatment-emergent adverse events [TEAEs]) in the RP2D population; characterization of GI and skin-related events in 114 PPP from a phase 1/2 study (NCT02716116); and clinical activity in PPP with and without dose reductions due to TEAEs.

RESULTS

In the RP2D population (N = 257), the most common TEAEs were diarrhea (93%), nausea (47%), rash (38%), and vomiting (37%). In PPP (N = 114), median times to diarrhea onset and resolution were 5 and 2 days, respectively. Median times to onset and resolution of skin-related events were 9 and 78 days, respectively. Among PPP with (n = 29) or without (n = 85) dose reductions due to TEAEs, overall response rates were 21% and 31% and median durations of response were 5.7 and 17.5 months, respectively.

CONCLUSIONS

GI and skin-related events are common with mobocertinib; minimizing dose reductions with proactive management may improve clinical outcomes.

TRIAL REGISTRATION

NCT02716116; NCT03807778.

Population pharmacokinetic/pharmacodynamic joint modeling of ixazomib efficacy and safety using data from the pivotal phase III TOURMALINE‐MM1 study in multiple myeloma patients

Ixazomib is an oral proteasome inhibitor approved in combination with lenalidomide and dexamethasone for the treatment of relapsed/refractory multiple myeloma (MM). Approval in the United States, Europe, and additional countries was based on results from the phase III TOURMALINE‐MM1 (C16010) study. Here, joint population pharmacokinetic/pharmacodynamic time‐to‐event (TTE) and discrete time Markov models were developed to describe key safety (rash and diarrhea events, and platelet counts) and efficacy (myeloma protein [M‐protein] and progression‐free survival [PFS]) outcomes observed in TOURMALINE‐MM1. Models reliably described observed safety and efficacy results; prior immunomodulatory drug therapy and race were significant covariates for diarrhea and rash events, respectively, whereas M‐protein dynamics were sufficiently characterized using TTE models of relapse and dropout. Moreover, baseline M‐protein was identified as a significant covariate for observed PFS. The developed framework represents an integrated approach to describing safety and efficacy with MM therapy, enabling the simulation of prospective trials and potential alternate dosing regimens.

Abstract 5424: Selection of RP3D of xevinapant in combination with CRT in patients with LA SCCHN

Xevinapant, an antagonist of Inhibitor of Apoptosis Proteins (IAPs) showed significant improvement in locoregional control at 18 months (LRC18; primary endpoint), overall survival (OS) and progression-free survival (PFS) at an oral dose of 200 mg/day given on days 1-14 every 3 weeks in combination with CRT versus CRT with placebo in a phase II trial in patients with high-risk LA SCCHN (NCT02022098). In the dose escalation (DE) part of NCT02022098, 200 mg/day was the maximum tolerated dose and a trend of dose-response for efficacy in the 100-300 mg/day dose range was observed. The phase III TrilynX study of xevinapant plus CRT in patients with LA SCCHN is currently enrolling (NCT04459715). Here we present the integrated rationale for the recommended phase III dose (RP3D) of xevinapant 200 mg/day based on all available clinical and preclinical data and modeling and simulation (M&S).

At the RP3D, ~95% of the patients are projected to have free trough concentrations above in vitro IC50 for cIAP1 degradation (a pharmacodynamic [PD] marker), based on a population (pop) PK M&S. In patients, average free concentration over the dosing interval at RP3D is similar to that associated with maximal efficacy in preclinical SCCHN models. Pop PK/PD M&S

suggests that maximal cIAP1 degradation is maintained in PBMCs with 100-200 mg/day doses during the 14-day dosing period, with a trend of dose-response for the partial cIAP1 degradation at the end of the 3-week cycle.

Exposure response (E-R) analyses were conducted based on the pooled datasets of DE and randomized parts of study NCT02022098 (n=62 treated with xevinapant). Logistic regressions showed that probabilities of LRC18, overall response, complete response, and the composite safety endpoint of “mucositis and/or dysphagia” increase with increasing exposure (p<0.05). Statistically significant E-R relationships were not discernible for any other evaluated safety endpoints or for PFS, OS, or duration of LRC. However, patients in higher exposure subgroups showed a longer duration of LRC.

In summary, integration of preclinical pharmacology, clinical efficacy and safety profiles, clinical PK/PD, popPK, and E-R analyses support the RP3D selection of xevinapant at 200 mg/day administered on days 1-14 every 3 weeks with concomitant CRT, allowing for successive dose reductions to 150 mg and 100 mg for management of toxicities.

Citation Format: Yulia Vugmeyster, Abhigyan Ravula, Elisabeth Rouits, Paul M. Diderichsen, Huub J. Kleijn, Kosalaram Goteti, Andreas Schroeder, Karthik Venkatakrishnan. Selection of RP3D of xevinapant in combination with CRT in patients with LA SCCHN [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5424.

Exposure-response analyses of sacituzumab govitecan (SG) efficacy and safety in patients (pts) with metastatic triple-negative breast cancer (mTNBC)

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Background: SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. SG is approved for pts with mTNBC who received ≥2 prior chemotherapies (> 1 in the metastatic setting). The relationships between exposure of SG, free SN-38, and total antibody (tAB) following SG administration and its efficacy and safety outcomes were evaluated in pts with mTNBC. Methods: Available exposure efficacy and safety outcomes from the mTNBC cohort of the phase 1/2 IMMU-132-01 study (relapsed/refractory pts; n = 24) and mTNBC pts from the phase 3 ASCENT study who had received ≥2 prior therapies (> 1 in the metastatic setting; n = 253) were analyzed. Pts in IMMU-132-01 received 8 or 10 mg/kg SG and pts in ASCENT received 10 mg/kg SG on d1 and d8, of every 21d cycle. Effect of exposure on CR, ORR and the evaluated adverse events (AEs) of vomiting, diarrhea, hypersensitivity reactions, nausea, and neutropenia were analyzed using logistic (CR, ORR) or ordinal logistic (AE) regression models while OS, PFS, time to first dose reduction and time to first dose delay were analyzed using Cox PH models. Several exposure metrics related to the PK of SG, free SN-38, and tAB were evaluated as predictors of SG efficacy and safety and the most statistically significant exposure metric was retained in the model; effect of other covariates was characterized within the modeling framework. Results: Higher values of the average exposure over the treatment duration (CAVG) for SG (CAVGSG) were significantly associated with an increase in the probability of CR and ORR and higher CAVG values for tAB (CAVGtAB) were significantly associated with longer OS and PFS. The probability of Grade ≥1 evaluated AEs, the risk of dose reductions and dose delays were found to increase significantly with increasing CAVGSG. Neutropenia was the only AE where the effect of exposure was significantly associated with the probability of Grade ≥3 evaluated AEs. No statistically significant associations between exposure and the probability of Grade 4 AEs were observed for any of the evaluated endpoints. The developed models were used to estimate the efficacy and safety outcomes for the 8 mg/kg vs 10 mg/kg SG dose levels and the results indicated a more favorable risk/benefit profile for the 10 mg/kg dose level driven by the higher estimated efficacy. Baseline Trop-2 expression level was not statistically correlated with magnitude of clinical response based on the limited available Trop-2 data. Conclusions: Exposure-response relationships were observed for all evaluated efficacy and safety endpoints for SG in patients with mTNBC, and the higher efficacy (as assessed by CR, ORR, OS and PFS) achieved with the exposures associated with the 10 mg/kg SG dose regimen and its manageable safety profile support the appropriateness of the approved regimen of SG. Clinical trial information: NCT02574455, NCT01631552.

Population pharmacokinetics of mobocertinib in healthy volunteers and patients with non-small cell lung cancer

Mobocertinib is an oral tyrosine kinase inhibitor approved for treatment of patients with locally advanced or metastatic non‐small cell lung cancer (mNSCLC) with epidermal growth factor receptor gene (EGFR) exon 20 insertion mutations whose disease has progressed on or after platinum‐based chemotherapy. This population pharmacokinetic (PK) analysis describes the PK of mobocertinib and its active metabolites, AP32960, and AP32914, using data from two phase I studies in healthy volunteers (n = 110) and two phase I/II studies in patients with mNSCLC (n = 317), including the pivotal phase I/II study. The plasma PK of mobocertinib, AP32960, and AP32914 were well‐characterized by a joint semimechanistic model that included two compartments for mobocertinib with absorption via three transit compartments, two compartments for AP32960, and one compartment for AP32914. The observed time‐dependency in PK was described by an enzyme compartment with drug and metabolite concentration‐dependent stimulation of enzyme production, resulting in the enzyme increasing the apparent clearance of mobocertinib, AP32960, and AP32914. Effects of healthy volunteer status (vs. patients with mNSCLC) on apparent oral clearance of all three moieties and on apparent central volume of distribution for mobocertinib were included as structural covariates in the final model. No clinically meaningful differences in mobocertinib PK were observed based on age (18–86 years), race, sex, body weight (37.3–132 kg), mild‐to‐moderate renal impairment (estimated glomerular filtration rate 30–89 ml/min/1.73 m² by modification of diet in renal disease equation), or mild‐to‐moderate hepatic impairment, suggesting that no dose adjustment is required based on these covariates in patients with mNSCLC.

Mobocertinib Dose Rationale in Patients with Metastatic NSCLC with EGFR Exon 20 Insertions: Exposure-Response Analyses of a Pivotal Phase I/II Study

Mobocertinib is an oral tyrosine kinase inhibitor approved for treatment of patients with locally advanced or metastatic non‐small cell lung cancer (mNSCLC) with epidermal growth factor receptor gene (EGFR) exon 20 insertion (ex20ins) mutations previously treated with platinum‐based chemotherapy. These exposure–response analyses assessed potential relationships between exposure and efficacy or safety outcomes in platinum‐pretreated patients with EGFRex20ins‐positive mNSCLC who received mobocertinib 160 mg once daily (q.d.) in a pivotal phase I/II study. A statistically significant relationship between the independent review committee‐assessed objective response rate and molar sum exposure to mobocertinib and its active metabolites (AP32960 and AP32914) was not discernable using a longitudinal model of clinical response driven by normalized dynamic molar sum exposure or a static model of best clinical response based on time‐averaged molar sum exposure. However, the longitudinal model suggested a trend for decreased probability of response with the change in mobocertinib molar sum exposure between the 160‐ and 120‐mg doses (odds ratio: 0.78; 95% confidence interval: 0.55–1.10; P = 0.156). Time‐averaged molar sum exposure was a significant predictor of the rate of grade ≥ 3 treatment‐emergent adverse events (AEs). Taken together, these exposure–efficacy and exposure–safety results support a favorable benefit‐risk profile for the approved mobocertinib 160‐mg q.d. dose and dose modification guidelines for patients experiencing AEs.

Population Pharmacokinetics of Ponatinib in Healthy Adult Volunteers and Patients With Hematologic Malignancies and Model-Informed Dose Selection for Pediatric Development

The BCR-ABL1 inhibitor ponatinib is approved for the treatment of adults with chronic myeloid leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia, including those with the T315I mutation. We report a population pharmacokinetic model-based analysis for ponatinib and its application to inform dose selection for pediatric development. Plasma concentration-time data were collected from 260 participants (86 healthy volunteers; 174 patients with hematologic malignancies) enrolled across 7 clinical trials. Data were analyzed using nonlinear mixed-effects modeling. Ponatinib pharmacokinetics were described by a 2-compartment model with first-order elimination from the central compartment. The final model included body weight and age as covariates on the apparent central volume of distribution; however, exposure variability explained by these covariates was small compared with overall variability in the population. None of the covariates evaluated, including sex, age (19-85 years), race, body weight (40.7-152.0 kg), total bilirubin (0.1-3.16 mg/dL), alanine aminotransferase (6-188 U/L), albumin (23.0-52.5 g/L), and creatinine clearance (≥28 mL/min) had clinically meaningful effects on apparent oral clearance. Simulations based on the final model predicted that daily doses of 15 to 45 mg result in steady-state average concentrations that are in the pharmacological range for BCR-ABL1 inhibition and approximate or exceed concentrations associated with suppression of T315I mutant clones. The final model was adapted using allometric scaling to inform dose selection for pediatric development. Clinicaltrials.gov identifier: NCT00660920; NCT01667133; NCT01650805.

Brigatinib Dose Rationale in Anaplastic Lymphoma Kinase-Positive Non-Small Cell Lung Cancer: Exposure-Response Analyses of Pivotal ALTA Study

Brigatinib is a kinase inhibitor indicated for patients with advanced anaplastic lymphoma kinase–positive non‐small cell lung cancer who progressed on or are intolerant to crizotinib. Approval was based on results from a randomized, dose‐ranging phase II study (ALK in Lung Cancer Trial of AP26113 (ALTA)). Despite an apparent dose–response relationship for efficacy in ALTA, an exposure–response relationship was not discernable using static models driven by time‐averaged exposure. However, exposure–response modeling using daily time‐varying area under the concentration curve as the predictor in time‐to‐event models predicted that increasing the dose of brigatinib (range, 30 mg once daily (q.d.) to 240 mg q.d.) would result in clinically meaningful improvements in progression‐free survival (PFS), intracranial PFS, and overall survival. Grade ≥ 2 rash and amylase elevation were predicted to significantly increase with brigatinib exposure. These results provided support for a favorable benefit‐risk profile with the approved dosing regimen (180 mg q.d. with 7‐day lead‐in at 90 mg) versus 90 mg q.d.

Meta-Analyses of Clinical Efficacy of Risankizumab and Adalimumab in Chronic Plaque Psoriasis: Supporting Evidence of Risankizumab Superiority

Risankizumab, an anti‐interleukin‐23 monoclonal antibody, achieved significantly (P < 0.001) greater Psoriasis Area and Severity Index (PASI) and static Physician Global Assessment (sPGA) clear or almost clear (0/1) responses than adalimumab in a phase III trial in patients with moderate‐to‐severe psoriasis. Meta‐analyses of the PASI 50, PASI 75, PASI 90, PASI 100, and sPGA0/1 responses after 16 weeks of treatment from eight (three for risankizumab and five for adalimumab) randomized, placebo‐controlled trials were conducted to estimate the efficacy difference between risankizumab and adalimumab. For PASI 75, PASI 90, PASI 100, and sPGA0/1 responses, the estimated effect differences (95% confidence interval) between risankizumab and adalimumab were 15.2% (10.1%, 20.4%), 23.7% (15.7%, 31.2%), 20.8% (13.0%, 28.7%), and 20.1% (13.7%, 26.1%), respectively. These results were consistent with the observed efficacy difference from the head‐to‐head phase III trial, which was not included in the meta‐analyses, providing independent, confirmatory evidence of the superior efficacy of risankizumab compared with adalimumab for treatment of moderate‐to‐severe psoriasis.

Model-Informed Drug Development for Ixazomib, an Oral Proteasome Inhibitor

Model‐informed drug development (MIDD) was central to the development of the oral proteasome inhibitor ixazomib, facilitating internal decisions (switch from body surface area (BSA)‐based to fixed dosing, inclusive phase III trials, portfolio prioritization of ixazomib‐based combinations, phase III dose for maintenance treatment), regulatory review (model‐informed QT analysis, benefit–risk of 4 mg dose), and product labeling (absolute bioavailability and intrinsic/extrinsic factors). This review discusses the impact of MIDD in enabling patient‐centric therapeutic optimization during the development of ixazomib.