A Phase I Clinical Study Comparing the Pharmacokinetics, Safety, and Immunogenicity of GB221 Injection and Trastuzumab (Herceptin®) in Healthy Chinese Adults.

BACKGROUND AND OBJECTIVE: GB221 is a recombinant humanized anti-HER2 monoclonal antibody. The purpose of this study was to evaluate the pharmacokinetic, safety, and immunogenicity of GB221 in healthy Chinese adults in comparison to trastuzumab (Herceptin®). METHODS: In this randomized, double-blind, parallel-group phase I clinical trial, 88 subjects were randomized 1:1 to receive a single intravenous infusion (90-100 min) of GB221 or trastuzumab (6 mg/kg). The primary pharmacokinetic parameters-maximum observed serum concentration (Cmax), area under the serum concentration-time curve from zero to the last quantifiable concentration at time t (AUC0-t), and area under the serum concentration-time curve from time zero to infinity (AUC0-∞)-of GB221 and trastuzumab were compared to establish whether the 90% confidence interval (CI) attained the 80-125% bioequivalence standard. Safety and immunogenicity were also evaluated. RESULTS: The GB221 group (n = 43) and the trastuzumab group (n = 44) showed similar pharmacokinetic characteristics. The geometric mean ratios (90% CI) of Cmax, AUC0-t, and AUC0-∞ between the two groups were 107.53% (102.25-113.07%), 108.31% (103.57-113.26%), and 108.34% (103.57-113.33%), respectively. The incidence of treatment-emergent adverse events (TEAEs) was 83.7% (36/43) of the subjects in the GB221 group and 95.5% (42/44) of the subjects in the trastuzumab group. No subjects withdrew from the trial due to TEAEs, and there were no occurrences of serious adverse events. All subjects tested negative for antidrug antibodies (ADA). CONCLUSION: GB221 demonstrated similar pharmacokinetics to trastuzumab and comparable safety and immunogenicity in healthy Chinese adults.

Targeting Breast Cancer Using 177 Lu-Labeled Trastuzumab and Trastuzumab Fragment : First-in-Human Clinical Experience.

PURPOSE: A monoclonal antibody, trastuzumab, is used for immunotherapy for HER2-expressing breast cancers. Large-sized antibodies demonstrate hepatobiliary clearance and slower pharmacokinetics. A trastuzumab fragment (Fab; 45 kDa) has been generated for theranostic use. PATIENTS AND METHODS: Fab was generated by papain digestion. Trastuzumab and Fab have been radiolabelled with 177 Lu after being conjugated with a bifunctional chelating. The affinity and target specificity were studied in vitro. The first-in-human study was performed. RESULTS: The bifunctional chelating agent conjugation of 1-2 molecules with trastuzumab and Fab was detected at the molar ratio 1:10 in bicarbonate buffer (0.5 M, pH 8) at 37°-40°C. However, 2-3 molecules of bifunctional chelating agent were conjugated when DMSO in PBS (0.1 M, pH 7) was used as a conjugation buffer at a molar ratio of 1:10. The radiolabelling yield of DOTA-conjugated Fab and trastuzumab at pH 5, 45°C to 50°C, with incubation time 2.5-3 hours was 80% and 41.67%, respectively. However, with DOTAGA-conjugated trastuzumab and Fab, the maximum radiolabelling yield at pH 5.5, 37°C, and at 2.5-3 hours was 80.83% and 83%, respectively. The calculated K d of DOTAGA Fab and trastuzumab with HER2-positive SKBR3 cells was 6.85 ± 0.24 × 10 -8 M and 1.71 ± 0.10 × 10 -8 M, respectively. DOTAGA-Fab and trastuzumab showed better radiolabelling yield at mild reaction conditions.177 Lu-DOTAGA-Fab demonstrated higher lesion uptake and lower liver retention as compared with 177 Lu-DOTAGA-trastuzumab. However, 177 Lu-DOTAGA-Fab as compared with 177 Lu-DOTAGA-trastuzumab showed a relatively early washout (5 days) from the lesion. CONCLUSIONS: 177 Lu-DOTAGA-Fab and trastuzumab are suitable for targeting the HER2 receptors.

Identification of ADME genes polymorphic variants linked to trastuzumab-induced cardiotoxicity in breast cancer patients: Case series of mono-institutional experience.

BACKGROUND: Long-term survival induced by anticancer treatments discloses emerging frailty among breast cancer (BC) survivors. Trastuzumab-induced cardiotoxicity (TIC) is reported in at least 5% of HER2+BC patients. However, TIC mechanism remains unclear and predictive genetic biomarkers are still lacking. Interaction between systemic inflammation, cytokine release and ADME genes in cancer patients might contribute to explain mechanisms underlying individual susceptibility to TIC and drug response variability. We present a single institution case series to investigate the potential role of genetic variants in ADME genes in HER2+BC patients TIC experienced. METHODS: We selected data related to 40 HER2+ BC patients undergone to DMET genotyping of ADME constitutive variant profiling, with the aim to prospectively explore their potential role in developing TIC. Only 3 patients ("case series"), who experienced TIC, were compared to 37 "control group" matched patients cardiotoxicity-sparing. All patients underwent to left ventricular ejection fraction (LVEF) evaluation at diagnosis and during anti-HER2 therapy. Each single probe was clustered to detect SNPs related to cardiotoxicity. RESULTS: In this retrospective analysis, our 3 cases were homogeneous in terms of clinical-pathological characteristics, trastuzumab-based treatment and LVEF decline. We identified 9 polymorphic variants in 8 ADME genes (UGT1A1, UGT1A6, UGT1A7, UGT2B15, SLC22A1, CYP3A5, ABCC4, CYP2D6) potentially associated with TIC. CONCLUSION: Real-world TIC incidence is higher compared to randomized clinical trials and biomarkers with potential predictive value aren't available. Our preliminary data, as proof of concept, could suggest a predictive role of pharmacogenomic approach in the identification of cardiotoxicity risk biomarkers for anti-HER2 treatment.

Cellular 1H MR Relaxation Times in Healthy and Cancer Three-Dimensional (3D) Breast Cell Culture.

Noninvasive measurements of 1H Magnetic Resonance Imaging (MR) relaxation times in a three-dimensional (3D) cell culture construct are presented. Trastuzumab was used as a pharmacological component delivered to the cells in vitro. The purpose of this study was to evaluate the Trastuzumab delivery by relaxation times in 3D cell cultures. The bioreactor has been designed and used for 3D cell cultures. Four bioreactors were prepared, two with normal cells and two with breast cancer cells. The relaxation times of HTB-125 and CRL 2314 cell cultures were determined. An immunohistochemistry (IHC) test was performed before MRI measurements to confirm the amount of HER2 protein in the CRL-2314 cancer cells. The results showed that the relaxation time of CRL2314 cells is lower than normal HTB-125 cells in both cases, before and after treatment. An analysis of the results showed that 3D culture studies have potential in evaluating treatment efficacy using relaxation times measurements with a field of 1.5 Tesla. The use 1H MRI relaxation times allows for the visualization of cell viability in response to treatment.

Comparing the pharmacokinetics, safety, and immunogenicity of HLX02 to US- and EU-approved trastuzumab in healthy Chinese male subjects: A Phase I, randomized, double-blind, parallel-group study.

BACKGROUND: HLX02, the first China-manufactured trastuzumab biosimilar, is approved in Europe (EU) and China. This study evaluated bioequivalence between HLX02 and US-approved trastuzumab (US-trastuzumab). METHOD: In this double-blind, parallel-group, Phase I study, healthy Chinese men were randomized (1:1:1) to receive a single 6 mg/kg dose of HLX02, reference US-trastuzumab, or reference EU-approved trastuzumab (EU-trastuzumab). Equivalence in PK profiles was demonstrated if the 90% confidence intervals (CIs) for the geometric mean ratio (GMR) for the difference between the least square means of the area under the curve (AUC) from time 0 to infinity (AUC∞) were 0.8-1.25. RESULTS: Pharmacokinetic profiles of the three trastuzumab products were similar in 111 Chinese men. Equivalence was confirmed between HLX02 and US-trastuzumab (GMR for AUC∞ 1.009, 90% CI 0.950-1.072); HLX02 and EU-trastuzumab (GMR for AUC∞ 1.068, 90% CI 1.005-1.135); and EU- and US-trastuzumab (GMR for AUC∞ 0.945, 90% CI 0.889-1004). Exploratory analysis of all other PK parameters also demonstrated equivalence between any two of the three trastuzumab products. HLX02 had similar safety and immunogenicity profiles to US- and EU-trastuzumab. CONCLUSION: HLX02 is bioequivalent to US-trastuzumab and EU-trastuzumab, with similar safety and immunogenicity profiles. US- and EU-trastuzumab were also bioequivalent to each other.

A Randomized, Single-dose, Phase I Clinical Comparison of a Trastuzumab Biosimilar With a Reference Trastuzumab Formulation in Healthy Chinese Male Volunteers.

The test drug, a recombinant humanized monoclonal antibody, is a biosimilar candidate for the reference drug. The purpose of this study was to evaluate the bioequivalence of these two drugs. The study was divided into two parts, a pre-study and a formal trial. The pre-study included two subjects who were each given a single intravenous infusion of 6 mg/kg test drug. The formal trial was designed to be a randomized, double-blind, parallel controlled trial in which 70 subjects were randomly assigned 1:1 to receive either test or reference drug as a single 6 mg/kg intravenous infusion. In the pre-study, the immunogenicity was negative in both subjects and the safety of the test drug was considered to be good. The two groups in the formal trial had similar demographic characteristics. The 90% confidence interval of geometric mean ratios of area under the serum concentration-time curve from the time 0 to the time of last quantifiable concentration, area under the serum concentration-curve from time 0 to infinity, and maximum observed serum concentration between the test group and the reference group fell between 80% and 125% and the bioequivalence was recognized. There was no significant difference in the positive rate of antidrug antibodies. The treatment-emergent adverse events in the test group were similar to those in the reference group. This study showed that the test drug has similar pharmacokinetics, immunogenicity, and safety to the reference drug in healthy male subjects.

Leveraging a Dual Variable Domain Immunoglobulin to Create a Site-Specifically Modified Radioimmunoconjugate.

Site-specifically modified radioimmunoconjugates exhibit superior in vitro and in vivo behavior compared to analogues synthesized via traditional stochastic methods. However, the development of approaches to site-specific bioconjugation that combine high levels of selectivity, simple reaction conditions, and clinical translatability remains a challenge. Herein, we describe a novel solution to this problem: the use of dual-variable domain immunoglobulins (DVD-IgG). More specifically, we report the synthesis, in vitro evaluation, and in vivo validation of a 177Lu-labeled radioimmunoconjugate based on HER2DVD, a DVD-IgG containing the HER2-targeting variable domains of trastuzumab and the catalytic variable domains of IgG h38C2. To this end, we first modified HER2DVD with a phenyloxadiazolyl methlysulfone-modified variant of the chelator CHX-A″-DTPA (PODS-CHX-A''-DTPA) and verified the site-specificity of the conjugation for the reactive lysines within the catalytic domains via chemical assay, MALDI-ToF mass spectrometry, and SDS-PAGE. The chelator-bearing immunoconjugate was subsequently labeled with [177Lu]Lu3+ to produce the completed radioimmunoconjugate, [177Lu]Lu-CHX-A″-DTPAPODS-HER2DVD, in >80% radiochemical conversion and a specific activity of 29.5 ± 7.1 GBq/µmol. [177Lu]Lu-CHX-A″-DTPAPODS-HER2DVD did not form aggregates upon prolonged incubation in human serum, displayed 87% stability to demetalation over a 7 days of incubation in serum, and exhibited an immunoreactive fraction of 0.95 with HER2-coated beads. Finally, we compared the pharmacokinetic profile of [177Lu]Lu-CHX-A″-DTPAPODS-HER2DVD to that of a 177Lu-labeled variant of trastuzumab in mice bearing subcutaneous HER2-expressing BT-474 human breast cancer xenografts. The in vivo performance of [177Lu]Lu-CHX-A″-DTPAPODS-HER2DVD matched that of 177Lu-labeled trastuzumab, with the former producing a tumoral activity concentration of 34.1 ± 12.1 %ID/g at 168 h and tumor-to-blood, tumor-to-liver, and tumor-to-kidney activity concentration ratios of 10.5, 9.6, and 21.8, respectively, at the same time point. Importantly, the DVD-IgG did not exhibit a substantially longer serum half-life than the traditional IgG despite its significantly larger size (202 kDa for the former vs 148 kDa for the latter). Taken together, these data suggest that DVD-IgGs represent a viable platform for the future development of highly effective site-specifically labeled radioimmunoconjugates for diagnostic imaging, theranostic imaging, and radioimmunotherapy.

Effect of Trastuzumab Deruxtecan on QT/QTc Interval and Pharmacokinetics in HER2-Positive or HER2-Low Metastatic/Unresectable Breast Cancer.

HER2-targeted anticancer therapies may be associated with cardiovascular adverse events. This study evaluated effects of the HER2-targeted antibody-drug conjugate trastuzumab deruxtecan (T-DXd, DS-8201a) on QT/QTc interval and its pharmacokinetics. Patients with heavily pretreated, metastatic HER2-expressing breast cancer were enrolled at seven study sites in Japan. T-DXd was administered intravenously at 6.4 mg/kg on day 1 of each 21-day cycle. Primary end points were baseline-adjusted QTcF interval and pharmacokinetics parameters. Key secondary end points included safety events, serum concentration of T-DXd and DXd at the time of electrocardiographic measurements, and antitumor activity parameters. Among 51 total patients, 47 (92.2%) had HER2-low breast cancer (immunohistochemistry 1+ or 2+ and in situ hybridization-negative/equivocal/missing). Pharmacokinetic parameters after a single dose of T-DXd were consistent with previous studies. After multiple doses, T-DXd showed moderate accumulation (accumulation ratio (cycle 3/cycle 1), 1.35), but DXd showed minimal accumulation (1.09). The upper bound of the 90% confidence interval for mean ΔQTcF interval was < 10 ms at all timepoints, and at mean maximum serum concentration was also < 10 ms. Based on concentration-QT analysis, ΔQTcF increased with increasing concentrations of T-DXd and DXd. No clinically meaningful QTcF prolongation was observed. T-DXd had a manageable safety profile and showed antitumor activity in HER2-low breast cancer. In this study, a T-DXd dose of 6.4 mg/kg, higher than the 5.4-mg/kg dose currently approved for breast cancer, was not associated with clinically relevant QTcF prolongation in heavily pretreated patients with HER2-expressing metastatic breast cancer. This study adds to our understanding of T-DXd for treatment of HER2-low breast cancer.

Population Pharmacokinetics of Patritumab Deruxtecan in Patients With Solid Tumors.

Patritumab deruxtecan is an antibody-drug conjugate consisting of a fully human monoclonal antibody against human epidermal growth factor receptor 3 (HER3) attached to a topoisomerase I inhibitor payload via a tetrapeptide-based cleavable linker. As part of the pharmacometric analysis informing dose selection for later-stage development, population pharmacokinetics (PK) analysis of patritumab deruxtecan was conducted with pooled serum PK data from patients with HER3-expressing solid tumors (from 3 phase 1/2 studies in breast, lung, and colorectal cancer; N = 425) treated over the dose range of 1.6 to 8.0 mg/kg intravenously every 3 weeks. Population PK modeling for deruxtecan (DXd)-conjugated antibody (representing patritumab deruxtecan) and unconjugated MAAA-1181a (DXd, payload) was carried out sequentially. DXd-conjugated antibody PK was described using a 2-compartment model with parallel linear and nonlinear clearance. Unconjugated DXd PK was described using a 1-compartment model with linear clearance and release of DXd as a first-order, time-dependent function of the level of DXd-conjugated antibody in the central compartment. Preliminary covariate evaluation was conducted for prespecified covariates of pharmacological plausibility and clinical interest. The final model retained weight (on linear clearance and central volume) and albumin level, sex, and tumor type (on linear clearance) for DXd-conjugated antibody, and weight (on release rate constant) and hepatic function (on clearance) for unconjugated DXd. Effects of these covariates on the exposure metrics were generally mild and did not require dose adjustment for subpopulations in subsequent development. Further PK characterization for patritumab deruxtecan will evolve with emerging data.

Effect of the Size of Protein Therapeutics on Brain Pharmacokinetics Following Systematic Administration.

Here, we have investigated the effect of size of protein therapeutics on brain pharmacokinetics (PK) following systemic administration in rats. All tested proteins were derived from trastuzumab that do not bind to any targets in rats. PK data generated with F(ab)2 (100 kDa), Fab (50 kDa), and scFv (27 kDa) fragments of trastuzumab, along with published PK data for FcRn non-binding and wild-type trastuzumab (150 kDa), were used to establish a relationship between the protein size and brain exposure. A large-pore microdialysis system was used to measure the PK of proteins in the plasma, the interstitial fluid (ISF) at the striatum (ST), and the cerebrospinal fluid (CSF) at the lateral ventricle (LV) and cisterna magna (CM). Concentrations of all the proteins in plasma, brain homogenate, ISF, and CSF were measured using ELISA. When evaluating the effect of protein size in the absence of FcRn binding, we found a bell-shaped relationship between the size and ISF/plasma AUC ratio, where 100 kDa F(ab)2 demonstrated the highest exposure. A similar bell-shaped relationship was observed for the brain homogenate/plasma AUC ratio, with a peak at 50 kDa. The CSF/plasma AUC ratio at LV increased monotonously with a decrease in the size of proteins. We observed that the exposure of protein therapeutics in different regions of the brain could be significantly different and there could be optimal sizes of protein therapeutics to accomplish maximum/selective exposure in selected brain regions following systemic administration.

Analytical and pharmacological consequences of the in vivo deamidation of trastuzumab and pertuzumab.

A liquid chromatography-tandem mass spectrometry method is presented for the quantitative determination of the in vivo deamidation of the biopharmaceutical proteins trastuzumab and pertuzumab at an asparagine in their complementarity determining regions (CDRs). For each analyte, two surrogate peptides are quantified after tryptic digestion of the entire plasma protein content: one from a stable part of the molecule, representing the total concentration, and one containing the deamidation-sensitive asparagine, corresponding to the remaining non-deamidated concentration. Using a plasma volume of 10 µL and a 2-h digestion at pH 7, concentrations between 2 and 1000 µg/mL can be determined for the various protein forms with values for bias and CV below 15% and without unacceptable in vitro deamidation taking place. A considerable difference between the total and non-deamidated concentrations, and thus a substantial degree of deamidation, was observed in plasma for both trastuzumab and pertuzumab. After a 56-day forced deamidation test 40% of trastuzumab and 68% of pertuzumab was deamidated, while trastuzumab and pertuzumab showed up to 47% and 35% of deamidation, respectively, in samples collected from breast cancer patients during treatment with a combination of both drugs. A good correlation between the non-deamidated concentration results and those of a receptor binding assay indicate a loss of receptor binding for both trastuzumab and pertuzumab along with the deamidation in their CDRs. Deamidated trastuzumab also lost its capability to inhibit the growth of breast cancer cells in a cell-based viability assay, suggesting a relation between the degree of deamidation and pharmacological activity.

Safety and pharmacokinetics of a new biosimilar trastuzumab (HL02): a Phase I bioequivalence study in healthy Chinese men.

OBJECTIVES: The study aimed to explore the bioequivalence of a proposed biosimilar HL02 vs. its reference products (US-trastuzumab) among healthy Chinese men. METHODS: In this study, nine healthy male subjects received single ascending doses of trastuzumab biosimilar (HL02, 2-8 mg/kg), and then a randomized, double-blind, two-arm, parallel study was conducted to investigate the PK similarity of HL02 (6 mg/kg) with that of US-trastuzumab as a reference drug. RESULTS: PK properties exhibited by HL02 (N = 55) were similar to those of US-trastuzumab (N = 52). The comparison of biosimilarity with US-trastuzumab showed that the 90% confidence intervals (CIs) of the ratios for Cmax, AUC0-t, and AUC0-∞ were within 80-125%. Nineteen subjects were positive for ADA and negative for NAb in both HL02 and US-trastuzumab groups. In total, 81.67% of subjects in HL02 and 78.95% in US-trastuzumab groups showed treatment-related mild or moderate adverse events, mild elevation of transaminase level being the most common adverse events (AE) recorded. CONCLUSIONS: The PK characteristics and immunogenicity exhibited by HL02 were similar to that of the reference product, US-trastuzumab. The safety profiles were similar in both the treatment groups with mild-moderate adverse effects.

Pharmacokinetics of Monoclonal Antibody and Antibody Fragments in the Mouse Eye Following Systemic Administration.

The ocular pharmacokinetics (PK) of antibody-based therapies are infrequently studied in mice due to the technical difficulties in working with the small murine eye. This study is the first of its kind to quantitatively measure the PK of variously sized proteins in the plasma, cornea/ICB, vitreous humor, retina, and posterior cup (including choroid) of the mouse and to evaluate the relationship between molecular weight (MW) and antibody biodistribution coefficient (BC) to the eye. Proteins analyzed include trastuzumab (150 kDa), trastuzumab-vc-MMAE (T-vc-MMAE, 155 kDa), F(ab)2 (100 kDa), Fab (50 kDa), and scFv (27 kDa). As expected, ocular PK mirrored the systemic PK as plasma was the driving force for ocular exposure. For trastuzumab, T-vc-MMAE, F(ab)2, Fab, and scFv, respectively, the BCs in the cornea/ICB were 0.610%, 0.475%, 1.74%, 3.39%, and 13.7%; the BCs in the vitreous humor were 0.0198%, 0.0427%, 0.0934%, 0.234%, and 5.56%; the BCs for the retina were 0.539%, 0.230%, 0.704%, 2.44%, and 20.4%; the BCs for the posterior cup were 0.557%, 0.650%, 1.47%, 4.06%, and 13.9%. The relationship between BC and MW was best characterized by a log-log regression in which BC decreased as MW increased, with every doubling in MW leading to a decrease in BC by a factor of 3.44 × , 6.76 × , 4.74 × , and 3.43 × in cornea/ICB, vitreous humor, retina, and posterior cup, respectively. In analyzing the disposition of protein therapeutics to the eye, these findings enhance our understanding of the potential for ocular toxicity of systemically administered protein therapeutics and may aid in the discovery of systemically administered protein therapeutics for ocular disorders.

A randomized, double-blind, single-dose study (LAVENDER) to assess the safety, tolerability, pharmacokinetics, and immunogenicity of a combined infusion of ABP 980 and pertuzumab in healthy subjects.

PURPOSE: ABP 980 (KANJINTI™) is a biosimilar to reference product HERCEPTIN® (trastuzumab RP). The goal of this study was to characterize the safety, tolerability, and immunogenicity of ABP 980 plus pertuzumab (PERJETA®) when co-administered in a single infusion bag in healthy subjects. METHODS: This randomized, double-blind, single-dose, 2-arm, parallel-group study (LAVENDER Study) evaluated an intravenous (IV) infusion of ABP 980 (6 mg/kg) plus pertuzumab (420 mg) combined in a single infusion bag relative to an IV infusion of trastuzumab RP (6 mg/kg) plus pertuzumab (420 mg) combined in a single infusion bag given over 60 min. The subjects were followed for 92 days post dosing. RESULTS: A total of 42 subjects were enrolled in the study and treated with investigational product. Due to an operational issue during dosing, the first 6 subjects enrolled in the study were replaced. A total of 36 randomized subjects, n = 18 for ABP 980 plus pertuzumab and n = 18 for trastuzumab RP plus pertuzumab, were treated. Resulting serum concentrations of ABP 980 and trastuzumab RP were similar. There were no serious adverse events, no deaths, and no cardiac disorders during the study. No subject developed anti-drug antibodies throughout the study. CONCLUSIONS: This study demonstrated the safety and tolerability of ABP 980 and pertuzumab admixture in a single infusion bag. The safety profiles and pharmacokinetic parameters of ABP 980 and pertuzumab were consistent with what is known for trastuzumab RP and pertuzumab. CLINICAL TRIAL LISTING: EudraCT 2018-002903-33.

Pharmacokinetics, Safety, and Efficacy of Trastuzumab Deruxtecan with Concomitant Ritonavir or Itraconazole in Patients with HER2-Expressing Advanced Solid Tumors.

PURPOSE: To evaluate drug-drug interactions between the human epidermal growth factor receptor 2 (HER2)-targeted antibody-drug conjugate trastuzumab deruxtecan (T-DXd; DS-8201a) and the OATP1B/CYP3A inhibitor ritonavir or the strong CYP3A inhibitor itraconazole. PATIENTS AND METHODS: Patients with HER2-expressing advanced solid tumors were enrolled in this phase I, open-label, single-sequence crossover study (NCT03383692) and received i.v. T-DXd 5.4 mg/kg every 3 weeks. Patients received ritonavir (cohort 1) or itraconazole (cohort 2) from day 17 of cycle 2 through the end of cycle 3. Primary endpoints were maximum serum concentration (C max) and partial area under the concentration-time curve from beginning of cycle through day 17 (AUC17d) for T-DXd and deruxtecan (DXd) with (cycle 3) and without (cycle 2) ritonavir or itraconazole treatment. RESULTS: Forty patients were enrolled (cohort 1, n = 17; cohort 2, n = 23). T-DXd C max was similar whether combined with ritonavir [cohort 1, cycle 3/cycle 2; 90% confidence interval (CI): 1.05 (0.98-1.13)] or itraconazole [cohort 2, 1.03 (0.96-1.09)]. T-DXd AUC17d increased from cycle 2 to 3; however, the cycle 3/cycle 2 ratio upper CI bound remained at ≤1.25 for both cohorts. For DXd (cycle 3/cycle 2), C max ratio was 0.99 (90% CI, 0.85-1.14) for cohort 1 and 1.04 (0.92-1.18) for cohort 2; AUC17d ratio was 1.22 (1.08-1.37) and 1.18 (1.11-1.25), respectively. The safety profile of T-DXd plus ritonavir or itraconazole was consistent with previous studies of T-DXd monotherapy. T-DXd demonstrated promising antitumor activity across HER2-expressing solid-tumor types. CONCLUSIONS: T-DXd was safely combined with ritonavir or itraconazole without clinically meaningful impact on T-DXd or DXd pharmacokinetics.

Physicochemical and functional characterization of trastuzumab-dkst, a trastuzumab biosimilar.

Aims: Preclinical comparative similarity studies of trastuzumab-dkst, a Herceptin® biosimilar, are reported. Materials & methods: Primary sequence and higher order structure and pharmacological mechanisms of action were compared using multiple techniques. Pharmacokinetics and repeat-dose toxicity were assessed in cynomolgus monkeys. Results: Primary structures were identical; secondary and tertiary structures were highly similar. Non-significant differences were observed for charge heterogeneity. Twelve of 13 glycan species were highly similar, with slightly higher total mannose levels in trastuzumab-dkst. FcγR and FcRn binding activity was highly similar. Each drug equally inhibited HER2+ cell proliferation, demonstrating equivalent relative potency in mediating HER2+ cell cytolysis by antibody-dependent cellular cytotoxicity. Pharmacokinetic and toxicological profiles in cynomolgus monkeys were similar. Conclusion: Trastuzumab-dkst, US-licensed trastuzumab and EU-approved trastuzumab demonstrate high structural and functional similarity.

Population pharmacokinetics and exposure-response relationship of trastuzumab and bevacizumab in early-stage breast cancer.

AIMS: To describe the sources of interindividual variability of bevacizumab and trastuzumab pharmacokinetics in early-stage breast cancer, and to study the relationship between exposure and both early clinical response and specific adverse events. PATIENTS AND METHODS: Patients (n = 86) received 6 cycles of docetaxel + trastuzumab. Early tumour response was assessed by determination of the maximum standard uptake value (SUVmax) variation (ΔSUVmax) after 1 cycle using [18F]-fluorodeoxyglucose (FDG) PET. Early poor responders (ΔSUVmax < 70%) also received bevacizumab from cycle 3 to cycle 6. Sources of interindividual variability in pharmacokinetics of both antibodies were studied by population compartment modelling. Exposure as assessed by area under the concentration-versus-time curve (AUC) was compared between responders and non-responders and between patients experiencing specific adverse events or not. RESULTS: A two-compartment model described the pharmacokinetics of both antibodies satisfactorily. Their central volume of distributions (Vc) increased with body surface area and their elimination half-lives were shorter (~14 days) than previously reported (~26-28 days). There was a time-dependent increase in trastuzumab Vc, positively correlated to baseline SUVmax. Bevacizumab elimination rate (k10) was positively correlated with ΔSUVmax measured at the end of the first cycle. Bevacizumab had no significantly influence on trastuzumab pharmacokinetics. No relationship between exposure and clinical response or occurrence of adverse events was found. CONCLUSION: Tumour uptake as assessed by SUVmax influences the pharmacokinetics of bevacizumab and trastuzumab. In early-stage breast cancer, elimination half-lives of these therapeutic monoclonal antibodies may be shorter than those previously reported in more advanced disease.

TROIKA-1: A double-blind, randomized, parallel group, study aimed to demonstrate the equivalent pharmacokinetic profile of HD201, a potential biosimilar candidate to trastuzumab, versus EU-Herceptin® and US-Herceptin® in healthy male subjects.

Prestige Biopharma Ltd (Singapore) has developed HD201, a proposed biosimilar to reference product trastuzumab. As a part of the stepwise approach to ensure comparability between the biosimilar candidate and the reference medicinal product, a phase I study in healthy subjects was conducted to demonstrate the pharmacokinetic (PK) equivalence (NCT03776240). The primary objective of the study was to demonstrate (PK) equivalence of HD201, EU-Herceptin® , and US-Herceptin® given at 6 mg/kg as a 90-min i.v. infusion to healthy male subjects. A pairwise comparisons based on the primary endpoint AUC0-inf and secondary PK endpoints, AUC0-last and Cmax were undertaken. PK equivalence was to be concluded if the 90% confidence interval (CI) for the ratio of geometric means for each criterion were within the equivalence margin of 80% to 125%. Secondary objectives included assessment of other PK parameters, safety, tolerability, and immunogenicity in the three arms. A total of 105 healthy male subjects (35/treatment) were randomized in this study. The 90% CI for the ratios of AUC0-inf , Cmax and AUC0-last , were within 80%-125% for the comparisons of HD201 to EU-Herceptin® or US-Herceptin® and EU-Herceptin® to US-Herceptin® . The frequency of subjects with TEAEs of special interest was slightly lower in the HD201 group (20.0%) compared to the other treatment groups (EU-Herceptin® : 34.3%; US-Herceptin® : 31.4%). Only 1 subject (EU-Herceptin® group) developed anti-drug antibodies prior to dosing. Overall, HD201 demonstrates PK similarity to both EU-Herceptin® and US-Herceptin® . The three study drugs also demonstrated similar safety profiles.

Two-pore physiologically based pharmacokinetic model validation using whole-body biodistribution of trastuzumab and different-size fragments in mice.

In the past, our lab proposed a two-pore PBPK model for different-size protein therapeutics using de novo derived parameters and the model was validated using plasma PK data of different-size antibody fragments digitized from the literature (Li Z, Shah DK, J Pharmacokinet Pharmacodynam 46(3):305-318, 2009). To further validate the model using tissue distribution data, whole-body biodistribution study of 6 different-size proteins in mice were conducted. Studied molecules covered a wide MW range (13-150 kDa). Plasma PK and tissue distribution profiles is 9 tissues were measured, including heart, lung, liver, spleen, kidney, skin, muscle, small intestine, large intestine. Tumor exposure of different-size proteins were also evaluated. The PBPK model was validated by comparing percentage predictive errors (%PE) between observed and model predicted results for each type of molecule in each tissue. Model validation showed that the two-pore PBPK model was able to predict plasma, tissues and tumor PK of all studied molecules relatively well. This model could serve as a platform for developing a generic PBPK model for protein therapeutics in the future.

Visualization of Intratumor Pharmacokinetics of [fam-] Trastuzumab Deruxtecan (DS-8201a) in HER2 Heterogeneous Model Using Phosphor-integrated Dots Imaging Analysis.

PURPOSE: We assessed the intratumor pharmacokinetics of [fam-] trastuzumab deruxtecan, T-DXd (known as DS-8201a), a novel HER2-targeted antibody-drug conjugate, using phosphor-integrated dots (PID)-imaging analysis to elucidate its pharmacologic mechanism. EXPERIMENTAL DESIGN: We used two mouse xenograft models administered T-DXd at the concentration of 4 mg/kg: (i) a heterogeneous model in which HER2-positive and HER2-negative cell lines were mixed, and (ii) a homogeneous model in which both cell types were transplanted separately into the same mouse. PID imaging involved immunostaining using novel high-intensity fluorescent nanoparticles. The distribution of T-DXd was assessed by PID imaging targeting the parent antibody, trastuzumab, and the payload, DXd, in serial frozen sections, respectively. RESULTS: After T-DXd administration in the heterogeneous model, HER2 expression tended to decrease in a time-dependent manner. The distribution of trastuzumab and DXd was observed by PID imaging along the HER2-positive area throughout the observation period. A detailed comparison of the PID distribution between trastuzumab and DXd showed that trastuzumab matched almost perfectly with the HER2-positive area. In contrast, DXd exhibited widespread distribution in the surrounding HER2-negative area as well. In the HER2-negative tumor of the homogeneous model, the PID distribution of trastuzumab and DXd remained extremely low throughout the observation period. CONCLUSIONS: Our results suggest that T-DXd is distributed to tumor tissues via trastuzumab in a HER2-dependent manner and then to adjacent HER2-negative areas. We successfully visualized the intratumor distribution of T-DXd and its mechanism of action, the so-called "bystander effect."