John Lu

Osteoprotegerin Ligand Modulates Murine Osteoclast Survival in Vitro and in Vivo

Osteoprotegerin ligand (OPGL) targets osteoclast precursors and osteoclasts to enhance differentiation and activation, however, little is known about OPGL effects on osteoclast survival. In vitro, the combination of OPGL + colony-stimulating factor-1 (CSF-1) is required for optimal osteoclast survival. Ultrastructurally, apoptotic changes were observed in detached cells and culture lysates exhibited elevated caspase 3 activity, particularly in cultures lacking CSF-1. DEVD-FMK (caspase 3 inhibitor) partially protected cells when combined with OPGL, but not when used alone or in combination with CSF-1. CSF-1 maintained NF-kappaB activation and increased the expression of bcl-2 and bcl-X(L) mRNA, but had no effect on JNK activation. In contrast, OPGL enhanced both NF-kappaB and JNK kinase activation and increased the expression of c-src, but not bcl-2 and bcl-X(L) mRNA. These data suggest that aspects of both OPGLs and CSF-1s signaling/survival pathways are required for optimal osteoclast survival. In mice, a single dose of OPG, the OPGL decoy receptor, led to a >90% loss of osteoclasts because of apoptosis within 48 hours of exposure without impacting osteoclast precursor cells. Therefore, OPGL is essential, but not sufficient, for osteoclast survival and endogenous CSF-1 levels are insufficient to maintain osteoclast viability in the absence of OPGL.

Cinacalcet Reduces Serum Calcium Concentrations in Patients with Intractable Primary Hyperparathyroidism

CONTEXT Patients with persistent primary hyperparathyroidism (PHPT) after parathyroidectomy or with contraindications to parathyroidectomy often require chronic treatment for hypercalcemia. OBJECTIVE The objective of the study was to assess the ability of the calcimimetic, cinacalcet, to reduce serum calcium in patients with intractable PHPT. DESIGN This was an open-label, single-arm study comprising a titration phase of variable duration (2-16 wk) and a maintenance phase of up to 136 wk. SETTING The study was conducted at 23 centers in Europe, the United States, and Canada. PATIENTS The study included 17 patients with intractable PHPT and serum calcium greater than 12.5 mg/dl (3.1 mmol/liter). INTERVENTION During the titration phase, cinacalcet dosages were titrated every 2 wk (30 mg twice daily to 90 mg four times daily) for 16 wk until serum calcium was 10 mg/dl or less (2.5 mmol/liter). If serum calcium increased during the maintenance phase, additional increases in the cinacalcet dose were permitted. MAIN OUTCOME MEASURE The primary end point was the proportion of patients experiencing a reduction in serum calcium of 1 mg/dl or greater (0.25 mmol/liter) at the end of the titration phase. RESULTS Mean +/- sd baseline serum calcium was 12.7 +/- 0.8 mg/dl (3.2 +/- 0.2 mmol/liter). At the end of titration, a 1 mg/dl or greater reduction in serum calcium was achieved in 15 patients (88%). Fifteen patients (88%) experienced treatment-related adverse events, none of which were serious. The most common adverse events were nausea, vomiting, and paresthesias. CONCLUSIONS In patients with intractable PHPT, cinacalcet reduces serum calcium, is generally well tolerated, and has the potential to fulfill an unmet medical need.

Epitope-Specific Mechanisms of IGF1R Inhibition by Ganitumab

Background Therapeutic antibodies targeting the IGF1R have shown diverse efficacy and safety signals in oncology clinical trials. The success of these agents as future human therapeutics depends on understanding the specific mechanisms by which these antibodies target IGF1R signaling. Methodology/Principal Findings A panel of well-characterized assays was used to investigate the mechanisms by which ganitumab, a fully human anti-IGF1R antibody undergoing clinical testing, inhibits IGF1R activity. Epitope mapping using IGF1R subdomains localized the ganitumab binding site to the L2 domain. Binding of ganitumab inhibited the high-affinity interaction of IGF-1 and IGF-2 required to activate IGF1R in cells engineered for IGF1R hypersensitivity and in human cancer cell lines, resulting in complete blockade of ligand-induced cellular proliferation. Inhibition of IGF1R activity by ganitumab did not depend on endosomal sequestration, since efficient ligand blockade was obtained without evidence of receptor internalization and degradation. Clinically relevant concentrations of ganitumab also inhibited the activation of hybrid receptors by IGF-1 and IGF-2. Ganitumab was not an agonist of homodimeric IGF1R or hybrid receptors in MCF-7 and COLO 205 cells, but low-level IGF1R activation was detected in cells engineered for IGF1R hypersensitivity. This activation seems biologically irrelevant since ganitumab completely inhibited ligand-driven proliferation. The in vivo efficacy profile of ganitumab was equivalent or better than CR and FnIII-1 domain-specific antibodies, alone or in combination with irinotecan. CR domain-specific antibodies only blocked IGF-1 binding to IGF1R but were more potent than ganitumab at inducing homodimer and hybrid receptor downregulation in vitro, however this difference was less obvious in vivo. No inhibition of hybrid receptors was observed with the FnIII-1 domain antibodies, which were relatively strong homodimer and hybrid agonists. Conclusions/Significance The safety and efficacy profile of ganitumab and other anti-IGF1R antibodies may be explained by the distinct molecular mechanisms by which they inhibit receptor signaling.

Discovery of 2,4-bis-arylamino-1,3-pyrimidines as insulin-like growth factor-1 receptor (IGF-1R) inhibitors

The insulin-like growth factor-1 receptor (IGF-1R) plays an important role in the regulation of cell growth and differentiation, and in protection from apoptosis. IGF-1R has been shown to be an appealing target for the treatment of human cancer. Herein, we report the synthesis, structure-activity relationships (SAR), X-ray cocrystal structure and in vivo tumor study results for a series of 2,4-bis-arylamino-1,3-pyrimidines.

Psychometric Evaluation of the FACT Colorectal Cancer Symptom Index (FCSI-9): Reliability, Validity, Responsiveness, and Clinical Meaningfulness

BACKGROUND Patient-reported outcomes (PROs) are essential for evaluating treatment effects on health-related quality of life and symptoms from the patients perspective. This study sought to evaluate the psychometric properties of the nine-item Functional Assessment of Cancer Therapy/National Comprehensive Cancer Network Colorectal Cancer Symptom Index (FCSI-9) in a metastatic colorectal cancer (mCRC) population. METHODS The FCSI-9 and EQ-5D were administered every 2-4 weeks to mCRC subjects in a phase III clinical trial. Three hundred ninety-one mCRC subjects completed the questionnaires at baseline and at least one follow-up assessment. Internal consistency reliability, test-retest reliability, construct validity, known groups validity, responsiveness, and the minimum important difference (MID) of the FCSI-9 were evaluated. RESULTS The internal consistency and test-retest reliability of the FCSI-9 were acceptable (0.81 and 0.76, respectively). Construct validity was supported based on moderate correlations with the EQ-5D. Known groups validity was evaluated by examining the FCSI-9 scores of subjects categorized by their Eastern Cooperative Oncology Group performance status (PS) score. Subjects with better PS scores reported significantly higher FCSI-9 scores than those with lower PS scores at both baseline and week 8. Responsiveness, as measured by Guyatts statistic, was 0.77 from baseline to week 8 and 0.60 from week 4 to week 12. Considering all data together, the MID of the FCSI-9 is estimated to be in the range of 1.5-3.0 points. CONCLUSION Results provide preliminary evidence of the reliability, validity, and responsiveness of the FCSI-9.