MEDI-573 as a novel approach to IGF-1R and IR-A signaling inhibition by blocking IGF ligands: Phase I PK/PD, safety data, and disease linkage studies in breast cancer

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Background: MEDI-573 is a dual-targeting human antibody that neutralizes IGF-I/-II ligands and inhibits IGF-1R and insulin receptor-A (IR-A) signaling pathways, which play a role in breast and other epithelial cancers. By sparing IR-B and its hybrid receptors, MEDI-573 is expected to achieve antitumor activity without perturbing glucose homeostasis.

Methods: In a 3 + 3 dose-escalation trial ( NCT00816361 ), patients with advanced solid tumors, KPS ≥ 60, received MEDI-573 as a weekly 1-hr IV infusion at 0.5, 1.5, 5, 10, or 15 mg/kg every 21 days. Objectives included determination of MTD, safety profile, pharmacokinetics (PK), pharmacodynamics, and tumor response. In a separate biomarker study, mRNA expression of IR-A and IR-B was compared in HR+/HER- breast cancers.

Results: Patients included 13M/12F (17 evaluable for efficacy at data cutoff); median age 59 yrs (range 37-78). No DLTs, drug-related SAEs, or significant toxicity patterns were reported. Forty-five AEs were considered treatment-related (% of patients): decreased appetite (28%), fatigue (24%), nausea (20%), diarrhea (16%), and anemia (12%). Hyperglycemia occurred in 2 patients, 1 with evidence of prestudy insulin resistance. No other significant changes in plasma glucose levels occurred. MEDI-573 had dose-proportionality, with AUC of 415 ± 165, 597 ± 298, and 1940 ± 904 d*μg/mL at 5, 10, and 15 mg/kg, respectively. Suppression of free IGF-1 and -2 was fully achieved at doses ≥ 5 mg/kg. Stable disease spanning ≥ 12 wks (range 12-36+) was seen in 6/17 patients. No antidrug antibodies were reported. In a study to identify breast cancer subsets that are dependent on IGF signaling, the IR-A:IR-B ratio was significantly higher in HR+/HER2- breast cancer than matched adjacent normal tissues and in proliferative luminal B than in luminal A breast cancer.

Conclusions: MEDI-573 showed acceptable safety and favorable PK profiles without significant changes in glucose levels. The IR-A:IR-B ratio supports a biomarker approach for MEDI-573 patient stratification. A biomarker-rich phase Ib/II study of MEDI-573 with an aromatase inhibitor in patients with advanced HR+/HER2- breast cancer opens in 2011.

The effects of paclitaxel (PTX) and 2-methoxyestradiol (2-ME2) on tumor oxygenation and HIF-1α in breast cancer

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Background: Radiation activates HIF-1a via a free radical mediated mechanism associated with reoxygenation. This response could be inhibited, resulting in reduced tumor vascularity and proliferation. Preclinical breast cancer models and a Phase Ib clinical trial (CT) were employed to look at the effects of chemo with or without an oral HIF-1a inhibitor, 2-ME2 (EntreMed) on tumor oxygenation and HIF-1a. Methods: Preclinical models of chemo effects on HIF-1a/oxygenation used 4T1 tumors and either doxorubicin (DOX) or cyclophosphamide (CTX). In addition, MDA-MB-231 tumors were treated with 2-ME2 (5days), and HIF-1a/MVD was assessed. In the CT, up to 15 pts with metastatic breast cancer, and biopsiable (>2 cm) non-bone sites were eligible. Tx was: D 1: PTX, 90 mg/m2; D 8: PTX, 90 mg/m2 with 2-ME2 (cohorts of 1,000/1,250/1,500 mg, qid). PTX was given 3 out of 4 wks. Bxs were done at enrollment, D8 (post-PTX), and D22 (post-PTX/2-ME2). Tumors were examined for changes in HIF-1a and CA9 levels, MVD, and genomic signatures of hypoxia. Plasma was obtained for osteoponin, PAI-1, and VEGF. Results: DOX and CTX both led to increases in HIF-1a, oxygenation, vascularity, and proliferation 4–10 days post treatment in the 4T1 model, while 2-ME2 reduced HIF-1a and MVD post treatment (5 d) in the MDA-MB-231 model. The CT opened in 6–2006, 9 pts have consented and 8 pts have undergone sequential biopsies and accrual continues. No DLT have been seen. Biopsy sites include chest wall, liver, and LN. Sufficient tissue/RNA/plasma has been obtained and the planned analyses will be presented. Conclusions: HIF-1a and tumor oxygenation appear to be modulated as a response to chemotherapy. The combination of PTX and 2-ME2 is clinically active, well-tolerated, and could serve as one of the first approaches to target HIF-1a in order to optimize therapy. Supported by Komen Grant BCTR0504044.

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The extravesicular domain of synaptotagmin-1 is released with the latent fibroblast growth factor-1 homodimer in response to heat shock

The heparin-binding fibroblast growth factor (FGF) prototypes lack a classical signal sequence, yet their presence is required in the extracellular compartment for the activation of cell-surface receptor-dependent signaling. Early studies with FGF-1 demonstrated its presence in bovine brain as a novel high molecular weight complex, and subsequent studies identified a second heparin-binding protein that co-purified with FGF-1. Polypeptide sequence analysis revealed that this heparin-binding protein corresponded to the extravesicular domain of bovine synaptotagmin (Syn)-1, a transmembrane component of synaptic vesicles involved in the regulation of organelle traffic. Since FGF-1 is released in response to heat shock as a mitogenically inactive Cys-30 homodimer, we sought to determine whether this heparin-binding protein was involved in the release of FGF-1. We report that a proteolytic fragment of the extravesicular domain of Syn-1 is associated with FGF-1 in the extracellular compartment of FGF-1-transfected NIH 3T3 cells following temperature stress. By using heparin-Sepharose affinity to discriminate between the monomer and homodimer forms of FGF-1 and resolution by conventional and limited denaturant gel shift immunoblot analysis, it was possible to identify FGF-1 and Syn-1 as potential components of a denaturant- and reducing agent-sensitive extracellular complex. It was also possible to demonstrate that the expression of an antisense-Syn-1 gene represses the release of FGF-1 in response to heat shock. These data indicate that FGF-1 may be able to utilize the cytosolic face of conventional exocytotic vesicles to traffic to the inner surface of the plasma membrane where it may gain access to the extracellular compartment as a complex with Syn-1.