Pharmacokinetics and Pharmacokinetic/Pharmacodynamic Properties of Rozibafusp alfa, a Bispecific Inhibitor of BAFF and ICOSL: Analyses of Phase 1 Clinical Trials

Rozibafusp alfa (AMG 570) is a first-in-class bispecific IgG2-peptide fusion designed to inhibit inducible T-cell costimulator ligand (ICOSL) and B-cell activating factor (BAFF). The pharmacokinetics (PK) and pharmacodynamics (PD) of rozibafusp alfa were investigated in two randomized, placebo-controlled clinical studies: a phase 1a single ascending-dose study (7-700 mg subcutaneously [SC]) in healthy subjects and a phase 1b multiple ascending-dose study (70-420 mg subcutaneously every 2 weeks [Q2W]) in patients with rheumatoid arthritis. Rozibafusp alfa exhibited nonlinear PK and dose-related and reversible dual-target engagement. Maximal reduction of naïve B cells from baseline (>40%), reflective of BAFF inhibition, was achieved with rozibafusp alfa exposure (AUC_inf and AUC_tau ) above 51 and 57 days•μg/mL for the single-dose (≥70 mg) and multiple-dose studies (≥70 mg Q2W), respectively. ICOSL receptor occupancy (RO) on circulating B cells, a surrogate PD endpoint for ICOSL inhibition, was directly related to drug concentration. PK/PD analysis showed >90% RO at rozibafusp alfa ≥22.2 μg/mL (≥420-mg single dose or ≥210 mg Q2W multiple dose), with saturation occurring at higher drug concentrations. These results informed the design and dose selection of a phase 2b study assessing the safety and efficacy of rozibafusp alfa in patients with active systemic lupus erythematosus.

Impact of Sotorasib on the Pharmacokinetics and Pharmacodynamics of Metformin, a MATE1/2K Substrate, in Healthy Subjects

BACKGROUND AND OBJECTIVE

The objectives of this study were to evaluate the effect of sotorasib on metformin pharmacokinetics and pharmacodynamics and the effect of metformin on sotorasib pharmacokinetics in healthy subjects. Sotorasib is an oral, small molecule inhibitor of the Kirsten rat sarcoma oncogene homolog (KRAS) G12C mutant protein (KRASG12C) protein approved by the U.S. Food and Drug Administration in 2021 for the treatment of KRASG12C-mutated locally advanced or metastatic non-small cell lung cancer (NSCLC) in adults who have received at least one prior systemic therapy METHODS: This was a phase I, single-center, open-label, three-period, fixed-sequence study. Subjects received single oral doses of metformin 850 mg, sotorasib 960 mg, and metformin 850 mg with sotorasib 960 mg. Urine and plasma were collected and assayed for metformin and sotorasib pharmacokinetics. Blood glucose was also measured for metformin pharmacodynamics. In addition, an in vitro study was conducted to determine whether sotorasib was an inhibitor of MATE1/2K or OCT2 transport.

RESULTS

Geometric least-squares mean ratio of sotorasib area under the concentration-time curve from time 0 to infinity and peak plasma concentration were 0.910 and 0.812, respectively, when sotorasib was coadministered with metformin compared with administration of sotorasib alone. Geometric least-squares mean ratio of metformin area under the concentration-time curve from time 0 to infinity and peak plasma concentration were 0.99 and 1.00, respectively, when comparing metformin coadministered with sotorasib to metformin alone. Geometric mean estimates of serum glucose area under the concentration-time curve from time 0 to 2 h following metformin alone, sotorasib alone, and metformin with sotorasib were 179, 222, and 194, respectively.

CONCLUSIONS

These results demonstrated that coadministration of metformin with sotorasib does not impact sotorasib exposure to a clinically significant extent. Coadministration of sotorasib with metformin does not affect metformin exposure or its antihyperglycemic effect, in contrast to the inhibitory effect observed in vitro. Doses of sotorasib 960 mg and metformin 850 mg were safe and well tolerated when coadministered to healthy subjects.

KRASG12C Inhibition with Sotorasib in Advanced Solid Tumors

BACKGROUND

No therapies for targeting KRAS mutations in cancer have been approved. The KRAS p.G12C mutation occurs in 13% of non-small-cell lung cancers (NSCLCs) and in 1 to 3% of colorectal cancers and other cancers. Sotorasib is a small molecule that selectively and irreversibly targets KRAS^G12C.

METHODS

We conducted a phase 1 trial of sotorasib in patients with advanced solid tumors harboring the KRAS p.G12C mutation. Patients received sotorasib orally once daily. The primary end point was safety. Key secondary end points were pharmacokinetics and objective response, as assessed according to Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1.

RESULTS

A total of 129 patients (59 with NSCLC, 42 with colorectal cancer, and 28 with other tumors) were included in dose escalation and expansion cohorts. Patients had received a median of 3 (range, 0 to 11) previous lines of anticancer therapies for metastatic disease. No dose-limiting toxic effects or treatment-related deaths were observed. A total of 73 patients (56.6%) had treatment-related adverse events; 15 patients (11.6%) had grade 3 or 4 events. In the subgroup with NSCLC, 32.2% (19 patients) had a confirmed objective response (complete or partial response) and 88.1% (52 patients) had disease control (objective response or stable disease); the median progression-free survival was 6.3 months (range, 0.0+ to 14.9 [with + indicating that the value includes patient data that were censored at data cutoff]). In the subgroup with colorectal cancer, 7.1% (3 patients) had a confirmed response, and 73.8% (31 patients) had disease control; the median progression-free survival was 4.0 months (range, 0.0+ to 11.1+). Responses were also observed in patients with pancreatic, endometrial, and appendiceal cancers and melanoma.

CONCLUSIONS

Sotorasib showed encouraging anticancer activity in patients with heavily pretreated advanced solid tumors harboring the KRAS p.G12C mutation. Grade 3 or 4 treatment-related toxic effects occurred in 11.6% of the patients. (Funded by Amgen and others; CodeBreaK100 ClinicalTrials.gov number, NCT03600883.).

The clinical KRAS(G12C) inhibitor AMG 510 drives anti-tumour immunity

KRAS is the most frequently mutated oncogene in cancer and encodes a key signalling protein in tumours^1,2. The KRAS(G12C) mutant has a cysteine residue that has been exploited to design covalent inhibitors that have promising preclinical activity^3-5. Here we optimized a series of inhibitors, using novel binding interactions to markedly enhance their potency and selectivity. Our efforts have led to the discovery of AMG 510, which is, to our knowledge, the first KRAS(G12C) inhibitor in clinical development. In preclinical analyses, treatment with AMG 510 led to the regression of KRAS^G12C tumours and improved the anti-tumour efficacy of chemotherapy and targeted agents. In immune-competent mice, treatment with AMG 510 resulted in a pro-inflammatory tumour microenvironment and produced durable cures alone as well as in combination with immune-checkpoint inhibitors. Cured mice rejected the growth of isogenic KRAS^G12D tumours, which suggests adaptive immunity against shared antigens. Furthermore, in clinical trials, AMG 510 demonstrated anti-tumour activity in the first dosing cohorts and represents a potentially transformative therapy for patients for whom effective treatments are lacking.

First-in-Human Study of PF-05212384 (PKI-587), a Small-Molecule, Intravenous, Dual Inhibitor of PI3K and mTOR in Patients with Advanced Cancer

PURPOSE

To evaluate safety (primary endpoint), tolerability, pharmacokinetics, pharmacodynamic profile, and preliminary activity of the intravenous, pan-class I isoform PI3K/mTOR inhibitor PF-05212384 in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Part 1 of this open-label phase I study was designed to estimate the maximum-tolerated dose (MTD) in patients with nonselected solid tumors, using a modified continual reassessment method to guide dose escalation. Objectives of part 2 were MTD confirmation and assessment of preliminary activity in patients with selected tumor types and PI3K pathway dysregulation.

RESULTS

Seventy-seven of the 78 enrolled patients received treatment. The MTD for PF-05212384, administered intravenously once weekly, was estimated to be 154 mg. The most common treatment-related adverse events (AE) were mucosal inflammation/stomatitis (58.4%), nausea (42.9%), hyperglycemia (26%), decreased appetite (24.7%), fatigue (24.7%), and vomiting (24.7%). The majority of patients treated at the MTD experienced only grade 1 treatment-related AEs. Grade 3 treatment-related AEs occurred in 23.8% of patients at the MTD. No treatment-related grade 4-5 AEs were reported at any dose level. Antitumor activity was noted in this heavily pretreated patient population, with two partial responses (PR) and an unconfirmed PR. Eight patients had long-lasting stable disease (>6 months). Pharmacokinetic analyses showed a biphasic concentration-time profile for PF-05212384 (half-life, 30-37 hours after multiple dosing). PF-05212384 inhibited downstream effectors of the PI3K pathway in paired tumor biopsies.

CONCLUSIONS

These findings demonstrate the manageable safety profile and antitumor activity of the PI3K/mTOR inhibitor PF-05212384, supporting further clinical development for patients with advanced solid malignancies.

Effect of axitinib on the QT interval in healthy volunteers

PURPOSE

Axitinib is a potent and selective inhibitor of vascular endothelial growth factor receptors 1-3, approved for second-line treatment of advanced renal cell carcinoma (RCC). Preclinical studies did not indicate potential for axitinib-induced delayed cardiac repolarization.

METHODS

The effect of axitinib on corrected QT (QTc) prolongation was evaluated with one-stage concentration-QTc response modeling using data from a definitive randomized crossover QT phase I study in healthy volunteers administered one single 5-mg axitinib dose alone or in the presence of steady-state ketoconazole (400 mg once daily).

RESULTS

Axitinib and ketoconazole had opposite effects on heart rate: Axitinib lowered it, ketoconazole raised it. The final analysis showed a flat relationship between QTc and axitinib concentration (slope -0.0314 ms·mL/ng) for axitinib alone. Mean highest placebo-matched change from baseline in QTc was -3.0 [90 % confidence interval (CI) -5.4, -0.6] ms. At supratherapeutic axitinib exposures achieved with potent cytochrome P450 3A4/5 inhibition by ketoconazole, the model predicted mean QTc change of 6.5 (90 % CI 4.4-8.5) ms. The slope population mean estimate was -0.331 (95 % CI -0.860, 0.198) ms·mL/µg for ketoconazole alone and 0.0725 (0.0445-0.1005) ms·mL/ng for axitinib in the presence of ketoconazole. The results were then compared with those obtained based on more widely used Fridericia's, Bazett's, and study-specific correction methods.

CONCLUSIONS

Since axitinib plasma concentrations observed in this study exceeded the range of concentrations observed in patients with RCC at the highest approved clinical dose (10 mg twice daily), axitinib was not associated with clinically significant QTc prolongation in target populations.

PKPD Modeling of VEGF, sVEGFR-2, sVEGFR-3, and sKIT as Predictors of Tumor Dynamics and Overall Survival Following Sunitinib Treatment in GIST

The predictive value of longitudinal biomarker data (vascular endothelial growth factor (VEGF), soluble VEGF receptor (sVEGFR)-2, sVEGFR-3, and soluble stem cell factor receptor (sKIT)) for tumor response and survival was assessed based on data from 303 patients with imatinib-resistant gastrointestinal stromal tumors (GIST) receiving sunitinib and/or placebo treatment. The longitudinal tumor size data were well characterized by a tumor growth inhibition model, which included, as significant descriptors of tumor size change, the model-predicted relative changes from baseline over time for sKIT (most significant) and sVEGFR-3, in addition to sunitinib exposure. Survival time was best described by a parametric time-to-event model with baseline tumor size and relative change in sVEGFR-3 over time as predictive factors. Based on the proposed modeling framework to link longitudinal biomarker data with overall survival using pharmacokinetic-pharmacodynamic models, sVEGFR-3 demonstrated the greatest predictive potential for overall survival following sunitinib treatment in GIST.CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e84; doi:10.1038/psp.2013.61; advance online publication 20 November 2013.

Standard Error of Empirical Bayes Estimate in NONMEM® VI

The pharmacokinetics/pharmacodynamics analysis software NONMEM® output provides model parameter estimates and associated standard errors. However, the standard error of empirical Bayes estimates of inter-subject variability is not available. A simple and direct method for estimating standard error of the empirical Bayes estimates of inter-subject variability using the NONMEM® VI internal matrix POSTV is developed and applied to several pharmacokinetic models using intensively or sparsely sampled data for demonstration and to evaluate performance. The computed standard error is in general similar to the results from other post-processing methods and the degree of difference, if any, depends on the employed estimation options.

A phase I study of PF-04929113 (SNX-5422), an orally bioavailable heat shock protein 90 inhibitor, in patients with refractory solid tumor malignancies and lymphomas

PURPOSE

To determine the maximum tolerated dose (MTD), toxicities, and pharmacokinetic/pharmacodynamic profile of the Hsp90 inhibitor PF-04929113 (SNX-5422) in patients with advanced solid tumors and lymphomas.

METHODS

This was a single-institution, phase I, dose-escalation study of PF-04929113 administered twice weekly. Endpoints included determination of dose-limiting toxicities (DLT), MTD, the safety profile of PF-04929113, pharmacodynamic assessment of PF-04929113 on Hsp70 induction, pharmacokinetic analysis of PF-04928473 (SNX-2112) and its prodrug PF-04929113, and assessment of response.

RESULTS

Thirty-three patients with advanced malignancies were treated. Dose escalation was continued up to 177 mg/m(2) administered orally twice a week. One DLT (nonseptic arthritis) was noted. No grade 4 drug-related adverse events were seen; grade 3 adverse events included diarrhea (9%), nonseptic arthritis (3%), aspartate aminotransferase elevation (3%), and thrombocytopenia (3%). No objective responses were seen in 32 evaluable patients. Fifteen patients (47%) had stable disease; 17 patients (53%) had progressive disease. Pharmacokinetic data revealed rapid absorption, hepatic, and extrahepatic clearance, extensive tissue binding, and almost linear pharmacokinetics of the active drug PF-04928473. Pharmacodynamic studies confirmed inhibition of Hsp90 and a linear correlation between pharmacokinetic parameters and Hsp70 induction.

CONCLUSIONS

PF-04929113 administered orally twice a week is well tolerated and inhibits its intended target Hsp90. No objective responses were seen, but long-lasting stabilizations were obtained. Although no clinically significant drug-related ocular toxicity was seen in this study, the development of PF-04929113 has been discontinued because of ocular toxicity seen in animal models and in a separate phase I study.

Determination of PF-04928473 in human plasma using liquid chromatography with tandem mass spectrometry

A simple, rapid and sensitive liquid chromatography/tandem mass spectrometric (LC/MS/MS) analytical method was developed for quantification of Hsp90 inhibitor PF-04928473 in human plasma, following administration of its prodrug, PF-04929113. Sample processing involved protein precipitation by addition of 0.4 mL of methanol containing internal standard (PF-04972487) to 50 μL volume of plasma sample. Chromatographic separation of PF-04928473 and PF-04972487 was achieved on a Phenomenex®) Luna C18(2) (2.0 mm x 50 mm, 5 μm) column using a gradient elution method with mobile phase solvents: methanol containing 0.1% formic acid and 0.1% formic acid at a flow rate of 0.25 mL/min. Detection was performed in electrospray positive ionization mode, monitoring the ion transitions from m/z 465.1→350.1 (PF-04928473) and m/z 447.0→329.1 (PF-04972487). The retention times for PF-04928473 and PF-04972487 were 1.86 and 2.85 min, respectively. Calibration curves were generated in the range of 2-2000 ng/mL. The accuracy and precision ranged from 94.1 to 99.0% and 86.7 to 97.6%, respectively, which were calculated using quality control samples of three different concentrations analyzed in quintuplicate on four different days.

Abstract A110: A phase 1 study of PF-04929113 (SNX5422), an orally bioavailable heat shock protein 90 (Hsp90) inhibitor administered twice weekly in patients with refractory solid tumor malignancies and lymphoma

Introduction: Hsp90 inhibitors have the potential for broad anti-cancer effects based on the spectrum of known client proteins and increased effect on mutations that drive malignant transformation and cancer growth. PF-04929113 (SNX5422; 113) is a novel, oral, non-antibiotic, selective Hsp90 inhibitor prodrug, with preclinical anti-tumor activity in multiple tumor models. The objective of this study was to evaluate the tolerability and describe the PK of 113 and its active moiety (PF- 04928473 /SNX2112; 473) in patients with refractory solid tumor malignancies and lymphoma.

Methods: Twenty-six subjects have been enrolled to date in this Phase 1, open-label, dose-escalation study. Subjects were treated with oral 113 twice weekly without interruption at doses ranging from 4 to 100 mg/m2. PBMCs were isolated and collected at baseline and various time points after-treatment. Cell lysates from PBMCs were assayed for Hsp70 and AKT protein level using Meso Scale Discovery (MSD) technology. Serial plasma concentrations of 473 were measured by LC-MS/MS after the first dose (Day 1) and after 6 doses (Day 18). PK parameters (mean ± standard deviation) were calculated using non-compartmental methods in WinNonlin v5.0.

Results: MTD for this schedule has not yet been reached. So far it has been well tolerated. Related adverse events were mainly low grade (most frequent nausea 31%) with grade ≥ 3 were reported in 8% (diarrhea and arthritis, 1 patient each). Based on results of interim pharmacokinetic analysis for doses 4 to 44 mg/m2, median time to 473 peak plasma concentrations was 2 h (range 0.33–4 h) and median half-life was ∼8.5h both at days 1 and 18. The median (range) CL/Fm at day 1 and day 18 were, 24.7 (12.9–81.2) L/hr and 22.6 (8.6–55.6) L/hr, respectively and was consistent across the dose range. Hsp70 was elevated with drug treatment, and further elevations were noted with increasing weekly dose. Although to date, no patients have achieved PR, several have experienced prolonged stable disease including medullary thyroid cancer (>450 days), lymphoma (>150 days), and esophagus, colon, adenoid cystic, lung carcinoid, and peritoneal mesothelioma (>100 days).

Conclusions: This schedule is well tolerated with no significant drug accumulation, few severe toxicities and potential for efficacy based on prolonged stable disease. Maximal concentrations of 113 were observed 2 h after oral administration of prodrug 113. Concentrations achieved were consistent with the preclinical activity. Accrual to the study to establish MTD is ongoing.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A110.

A population pharmacokinetic meta-analysis of sunitinib malate (SU11248) and its primary metabolite (SU12662) in healthy volunteers and oncology patients

PURPOSE

Sunitinib malate is an oral multitargeted tyrosine kinase inhibitor approved for advanced renal cell carcinoma and imatinib-resistant or imatinib-intolerant gastrointestinal stromal tumor. Following administration, sunitinib is metabolized by cytochrome P450 3A4 to an active metabolite (SU12662). The objective of this analysis was to assess sunitinib and SU12662 pharmacokinetics and to identify covariates that might explain variability in exposure following oral administration.

EXPERIMENTAL DESIGN

Data from 590 subjects (73 volunteers and 517 patients) in 14 studies were analyzed. Plasma concentration-time data were analyzed using nonlinear mixed-effects modeling to estimate population pharmacokinetic parameters, as well as relationships between these parameters and gender, race, age, weight, creatinine clearance, Eastern Cooperative Oncology Group score, and tumor type. Simulations were done to determine the predicted effect of these covariates on exposure.

RESULTS

Separate models were developed for sunitinib and SU12662 (each a two-compartment model with first-order absorption and elimination). Sunitinib parameters were estimated as CL/F, 51.8 L/h and Vd/F(central), 2,030 liters. SU12662 parameters were estimated as CL/F, 29.6 L/h and Vd/F(central), 3,080 liters. Tumor type (except acute myeloid leukemia), Asian race, gender, body weight, and elevated Eastern Cooperative Oncology Group score described a portion of the variability in CL/F for sunitinib and metabolite; gender and body weight explained some of the variability in Vd/F(central) for sunitinib and metabolite. Among patients, the predicted changes in sunitinib and metabolite AUC and C(max) as a result of the individual covariates ranged up to 17%.

CONCLUSION

The magnitude of the predicted changes in exposure with the covariates studied minimizes the necessity for dose adjustment in any of these subpopulations.

Pharmacokinetics of plasmid DNA in the rat

PURPOSE

The pharmacokinetics of plasmid DNA after IV bolus administration in the rat by following supercoiled (SC), open circular (OC), and linear (L) pDNA forms of the plasmid.

METHODS

SC, OC, and L pDNA were injected at 2,500, 500, 333, and 250 microg doses. The concentrations in the bloodstream of OC and L pDNA were monitored.

RESULTS

SC pDNA was detectable in the bloodstream only after a 2,500 microg dose, and had a clearance of 390(+/-50) ml/min and Vd of 81(+/-8) ml. The pharmacokinetics of OC pDNA exhibited non-linear characteristics with clearance ranging from 8.3(+/-0.8) to 1.3(+/-0.2) ml/min and a Vd of 39(+/-19) ml. L pDNA was cleared at 7.6(+/-2.3) ml/min and had a Vd of 37(+/-17) ml. AUC analysis revealed that 60(+/-10) % of the SC was converted to the OC form, and nearly complete conversion of the OC pDNA to L pDNA. Clearance of SC pDNA was decreased after liposome complexation to 87(+/-30) ml/min. However the clearance of OC and L pDNA was increased relative to naked pDNA at an equivalent dose to 37(+/-9) ml/min and 95(+/-37) ml/min respectively.

CONCLUSIONS

SC pDNA is rapidly metabolized and cleared from the circulation. OC pDNA displays non-linear pharmacokinetics. Linear pDNA exhibits first order kinetics. Liposome complexation protects the SC topoform, but the complexes are more rapidly cleared than the naked pDNA.

Kinetic modeling of plasmid DNA degradation in rat plasma

A major obstacle in gene delivery is the transport of intact plasmid DNA (pDNA) to target sites. We sought to investigate the kinetic processes underlying the degradation of pDNA in a rat plasma model, as this is one of the main components responsible for the clearance of pDNA after intravenous administration. We further sought to construct a complete kinetic model to describe the degradation of all three topoforms (supercoiled, open circular, and linear) of pDNA in a rat plasma model. Supercoiled pDNA was incubated in isolated rat plasma at 37 degrees C in vitro. At various time points, the plasma was assayed by electrophoresis for the amounts of supercoiled, open circular, and full-length linear pDNA remaining. The calculated amounts remaining were fit to linear differential equations describing this process. In this model, pDNA degradation is considered to be a unidirectional process, with supercoiled degrading to open circular and then to the linear topoform. The calculated kinetic parameters suggested that supercoiled pDNA degrades in rat plasma with a half-life of 1.2 minutes, open circular pDNA degrades with a half-life of 21 minutes, and linear pDNA degrades with a half-life of 11 minutes. Complexation of pDNA with liposomes resulted in a portion of the supercoiled plasmid remaining detectable through 5.5 hours.