Population Pharmacokinetics and Exposure-Response Relationship of Luspatercept, an Erythroid Maturation Agent, in Anemic Patients With ß-Thalassemia.

ß-Thalassemia is an inherited blood disorder resulting from defects in hemoglobin production, leading to premature death of red blood cells (RBCs) or their precursors. Patients with transfusion-dependent ß-thalassemia often need lifelong regular RBC transfusions to maintain adequate hemoglobin levels. Frequent transfusions may lead to iron overload and organ damage. Thus, there is a large unmet need for alternative therapies. Luspatercept, a first-in-class erythroid maturation agent, is the first approved therapy in the United States for the treatment of anemia in adult patients with ß-thalassemia who require regular RBC transfusions. The population pharmacokinetics and exposure-response relationship of luspatercept were evaluated in 285 patients with ß-thalassemia. Luspatercept displayed linear and time-invariant pharmacokinetics when administered subcutaneously once every 3 weeks. Body weight was the only clinically relevant covariate of luspatercept clearance, favoring weight-based dosing. Magnitude and frequency of hemoglobin increase, if not influenced by RBC transfusions, was positively correlated with luspatercept area under the serum concentration-time curve (AUC), 0.2-1.25 mg/kg, whereas a significant reduction in RBC units transfused was observed in frequently transfused patients. The probability of achieving ≥33% or ≥50% reduction in RBC transfusion burden was similar across the time-averaged AUC (0.6-1.25 mg/kg), with the 1 mg/kg starting dose sufficient for most early responders (71%-80%). Increasing luspatercept AUC (0.2-1.25 mg/kg) did not increase incidence or severity of treatment-emergent adverse events. These results provide a positive benefit-risk profile for the recommended luspatercept doses (1-1.25 mg/kg) in treating adult patients with ß-thalassemia who require regular RBC transfusions.

Population Pharmacokinetics and Exposure-Response of Luspatercept, an Erythroid Maturation Agent, in Anemic Patients With Myelodysplastic Syndromes.

Luspatercept is a recombinant fusion protein that enhances late-stage erythroid maturation. This report describes the population pharmacokinetics and exposure-response relationship of luspatercept in 260 patients with anemia due to myelodysplastic syndromes. Luspatercept displayed linear and time-invariant pharmacokinetics over a dose range of 0.125-1.75 mg/kg administered subcutaneously once every 3 weeks. Body weight was the only clinically relevant covariate of luspatercept exposure, supporting the weight-based dosing. The probability of achieving transfusion independence ≥ 8 weeks increased with time-averaged luspatercept serum exposure, reaching the plateau at doses 1.0-1.75 mg/kg. The probability of achieving multiple efficacy end points increased with slower luspatercept clearance, independent of effects of luspatercept exposure or disease characteristics. The probability of experiencing severe treatment-emergent adverse events decreased with increasing luspatercept exposure, especially during long-term treatment. These results provide a positive benefit-risk profile for the titration-to-response dose regimen (1.0-1.75 mg/kg) recommended for this population.

Development and characterization of a preclinical ovarian carcinoma model to investigate the mechanism of acquired resistance to trastuzumab.

Trastuzumab (Herceptin®) is a humanized monoclonal antibody designed to bind and inhibit the function of the human epidermal growth factor receptor 2 (HER2)/erbB2 receptor. Trastuzumab has demonstrated clinical activity in several types of HER2-overexpressing epithelial tumors, such as breast and metastatic gastric or gastroesophageal junction cancer. Relapse and therapeutic resistance, however, still occur in a subset of patients treated with regimens including trastuzumab, despite significant improvements in response rates, survival and quality of life. To investigate the potential mechanisms of acquired therapeutic resistance to trastuzumab, we developed a preclinical model of human ovarian cancer cells, SKOV-3 Herceptin-resistant (HR), and examined the corresponding changes in gene expression profiles. SKOV-3 HR cells were developed by in vivo serial passaging of parental trastuzumab-sensitive SKOV-3 cells. Following four rounds of serial transplantation of 'break-through' xenograft tumors under trastuzumab treatment, significant and reproducible differences in the effects of trastuzumab treatment between SKOV-3 HR and SKOV-3 cells in vivo and in vitro were revealed. SKOV-3 HR cells retained HER2 protein expression but were unaffected by the antiproliferative effects of trastuzumab. The trastuzumab binding affinity for SKOV-3 HR cells was diminished, despite these cells having more binding sites for trastuzumab. Microarray expression profiling (MEP) was performed to determine the genes involved in the resistance mechanism. Functional analysis revealed the differential expression of genes potentially involved in angiogenesis, metastasis, differentiation and proliferation, such as mucin1 (MUC1). Immunohistochemical staining of SKOV-3 HR cells demonstrated a marked overexpression of MUC1. Based on these data, we hypothesize that the overexpression of MUC1 may hinder trastuzumab binding to HER2 receptors, abrogating the antitumor effects of trastuzumab and thus could contribute to resistance to therapy. Moreover, the resultant MEP preclinical gene signature in this preclinical model system may provide the basis for further investigation of potential clinical mechanisms of resistance to trastuzumab.

Preclinical biomarkers for a cyclin-dependent kinase inhibitor translate to candidate pharmacodynamic biomarkers in phase I patients.

A genomics-based approach to identify pharmacodynamic biomarkers was used for a cyclin-dependent kinase inhibitory drug. R547 is a potent cyclin-dependent kinase inhibitor with a potent antiproliferative effect at pharmacologically relevant doses and is currently in phase I clinical trials. Using preclinical data derived from microarray experiments, we identified pharmacodynamic biomarkers to test in blood samples from patients in clinical trials. These candidate biomarkers were chosen based on several criteria: relevance to the mechanism of action of R547, dose responsiveness in preclinical models, and measurable expression in blood samples. We identified 26 potential biomarkers of R547 action and tested their clinical validity in patient blood samples by quantitative real-time PCR analysis. Based on the results, eight genes (FLJ44342, CD86, EGR1, MKI67, CCNB1, JUN, HEXIM1, and PFAAP5) were selected as dose-responsive pharmacodynamic biomarkers for phase II clinical trials.

A selective phosphatase of regenerating liver phosphatase inhibitor suppresses tumor cell anchorage-independent growth by a novel mechanism involving p130Cas cleavage.

The phosphatase of regenerating liver (PRL) family, a unique class of oncogenic phosphatases, consists of three members: PRL-1, PRL-2, and PRL-3. Aberrant overexpression of PRL-3 has been found in multiple solid tumor types. Ectopic expression of PRLs in cells induces transformation, increases mobility and invasiveness, and forms experimental metastases in mice. We have now shown that small interfering RNA-mediated depletion of PRL expression in cancer cells results in the down-regulation of p130Cas phosphorylation and expression and prevents tumor cell anchorage-independent growth in soft agar. We have also identified a small molecule, 7-amino-2-phenyl-5H-thieno[3,2-c]pyridin-4-one (thienopyridone), which potently and selectively inhibits all three PRLs but not other phosphatases in vitro. The thienopyridone showed significant inhibition of tumor cell anchorage-independent growth in soft agar, induction of the p130Cas cleavage, and anoikis, a type of apoptosis that can be induced by anticancer agents via disruption of cell-matrix interaction. Unlike etoposide, thienopyridone-induced p130Cas cleavage and apoptosis were not associated with increased levels of p53 and phospho-p53 (Ser(15)), a hallmark of genotoxic drug-induced p53 pathway activation. This is the first report of a potent selective PRL inhibitor that suppresses tumor cell three-dimensional growth by a novel mechanism involving p130Cas cleavage. This study reveals a new insight into the role of PRL-3 in priming tumor progression and shows that PRL may represent an attractive target for therapeutic intervention in cancer.

A phase I clinical and pharmacokinetic study of Ro 31-7453 given as a 7- or 14-day oral twice daily schedule every 4 weeks in patients with solid tumors.

PURPOSE: This is a dose-finding Phase I study of oral Ro 31-7453, a new class of antimitotic drug with promising preclinical activity in several chemoresistant models. EXPERIMENTAL DESIGN: Two schedules of oral Ro 31-7453 (every 12 h) given for either 7 or 14 consecutive days repeated every 4 weeks were explored consecutively. RESULTS: Thirty-seven patients with refractory cancer entered the study (14 on the 7-day schedule and 23 on the 14-day schedule). Median age was 63 years (range, 40-77 years), and median Karnofsky performance status was 80 (range, 60-100); the most frequent diagnosis was colorectal carcinoma (16 patients). Dose levels of 100, 200, 240, and 280 mg/m(2) twice daily (bid) for 7 days and 70, 100, 125, and 150 mg/m(2) bid for 14 days were explored. A total of 110 cycles were administered, the median number of cycles received was 3 (range, 1-7); six patients completed 6 or more cycles. Myelosuppression and mucositis were dose-limiting with both schedules. Fatigue and gastrointestinal toxicities other than mucositis were frequent but generally mild. The maximum tolerated doses were 200 mg/m(2) bid and 125 mg/m(2) bid for the 7- and 14-day schedules, respectively. Pharmacokinetic analysis showed rapid absorption and metabolism. The area under the concentration-time curve and trough concentrations of Ro 31-7453 and two active metabolites appeared dose proportional with a t(1/2) of approximately 9 h and a t(max) of approximately 4 h. One patient with pretreated lung cancer had a partial response. CONCLUSIONS: Both Ro 31-7453 regimens were feasible, but the 14-day schedule at the recommended dose of 125 mg/m(2) bid was selected for further monotherapy Phase II evaluation because of its higher preclinical activity. This regimen is convenient, well tolerated, and has a favorable pharmacokinetic profile.