Phase I dose escalation study of 12b80 (hydroxybisphosphonate linked doxorubicin) in naturally occurring osteosarcoma.

PURPOSE: 12b80 combines doxorubicin bound to a bone targeting hydroxybisphosphonate vector using a pH-sensitive linker, designed to specifically trigger doxorubicin release in an acidic bone tumor microenvironment. This phase I study aimed to determine the safety and toxicity profiles of 12b80 in dogs with naturally occurring osteosarcoma, with the objective to translate findings from dogs to humans. EXPERIMENTAL DESIGN: Ten client-owned dogs with osteosarcoma were enrolled in an accelerated dose-titration design followed by 3 + 3 design. Dogs received three cycles of 12b80 intravenous injection at 4 mg/kg (n = 1), 6 mg/kg (n = 2), 8 mg/kg (n = 3), and 10 mg/kg (n = 4). Endpoints included safety, tolerability, maximum tolerated dose (MTD), and dose-limiting toxicity (DLT). RESULTS: The MTD of 12b80 was 8 mg/kg (i.e., equivalent dose of doxorubicin of 110 mg/m2, range: 93-126). Most adverse events included grade ≤ 2 gastrointestinal disorders and hypersensitivity reactions. No hematological or cardiac DLT were observed at any dose tested. CONCLUSIONS: In dogs, 12b80 is overall well tolerated and expends the MTD of doxorubicin up to four times the standard dose of 30 mg/m2. These results demonstrate the potential therapeutic benefit of 12b80 in canine and human osteosarcoma.

12b80 - Hydroxybisphosphonate Linked Doxorubicin: Bone Targeted Strategy for Treatment of Osteosarcoma.

To reply to as yet unmet medical needs to treat osteosarcoma, a form of primary bone cancer, we conceived the 12b80 compound by covalently conjugating antineoplastic compound doxorubicin to a bone targeting hydroxybisphosphonate vector and turned it into a prodrug through a custom linker designed to specifically trigger doxorubicin release in acidic bone tumor microenvironment. Synthesis of 12b80 was thoroughly optimized to be produced at gram scale. 12b80 was evaluated in vitro for high bone support affinity, specific release of doxorubicin in acidic condition, lower cytotoxicity, and cellular uptake of the prodrug. In vivo in rodents, 12b80 displayed rapid and sustained targeting of bone tissue and tumor-associated heterotopic bone and permitted a higher doxorubicin payload in tumor bone environment compared to nonvectorized doxorubicin. Consequently, 12b80 showed much lower toxicity compared to doxorubicin, promoted strong antitumor effects on rodent orthotopic osteosarcoma, displayed a dose-response therapeutic effect, and was more potent than doxorubicin/zoledronate combination.

Synthesis and antiproliferative activity of ligerin and new fumagillin analogs against osteosarcoma.

Ligerin (1) is a natural chlorinated merosesquiterpenoid related to fumagillin (2) exhibiting a selective antiproliferative activity against osteosarcoma cell lines and an in vivo antitumor activity in a murine model. Semisynthesis of ligerin analogs was performed in order to study the effects of the C3-spiroepoxide substitution by a halogenated moiety together with the modulation of the C6 chain. Results showed that all derivatives exhibited an in vitro antiproliferative activity against osteosarcoma cell lines and that chlorohydrin compounds were equally or more active than their spiroepoxy analogs. Among semisynthetic analogs, the parent compound 1 was the best candidate for further studies since it exhibited higher or equivalent activity compared to TNP470 (3) against SaOS2 and MG63 human osteosarcoma cells with a four times weaker toxicity against HFF2 human fibroblasts. Quantitative videomicroscopy analysis was conducted and allowed a better understanding of the mechanism of its antiproliferative activity.

New chondrosarcoma cell lines and mouse models to study the link between chondrogenesis and chemoresistance.

Chondrosarcomas are cartilage-forming, poorly vascularized tumors. They represent the second malignant primary bone tumor of adults after osteosarcoma, but in contrast to osteosarcoma they are resistant to chemotherapy and radiotherapy, surgical excision remaining the only therapeutic option. Few cell lines and animal models are available, and the mechanisms behind their chemoresistance remain largely unknown. Our goal was to establish new cell lines and animal cancer models from human chondrosarcoma biopsies to study their chemoresistance. Between 2007 and 2012, 10 chondrosarcoma biopsies were collected and used for cell culture and transplantation into nude mice. Only one transplanted biopsy and one injected cell line has engrafted successfully leading to conventional central high-grade chondrosarcoma similar to the original biopsies. In culture, two new stable cell lines were obtained, one from a dedifferentiated and one from a grade III conventional central chondrosarcoma biopsy. Their genetic characterization revealed triploid karyotypes, mutations in IDH1, IDH2, and TP53, deletion in CDKN2A and/or MDM2 amplification. These cell lines expressed mesenchymal membrane markers (CD44, 73, 90, 105) and were able to produce a hyaline cartilaginous matrix when cultured in chondrogenic three-dimensional (3D) pellets. Using a high-throughput quantitative RT-PCR approach, we observed that cell lines cultured in monolayer had lost expression of several genes implicated in cartilage development (COL2A1, COMP, ACAN) but restored their expression in 3D cultures. Chondrosarcoma cells in monolayer were sensitive to several conventional chemotherapeutic agents but became resistant to low doses of mafosfamide or doxorubicin when cultured in 3D pellets, in parallel with an altered nucleic accumulation of the drug. Our results indicate that the cartilaginous matrix produced by chondrosarcoma cells may impair diffusion of several drugs and thus contribute to chemoresistance. Therefore, 3D chondrogenic cell pellets constitute a more relevant model to study chondrosarcoma chemoresistance and may be a valuable alternative to animal experimentations.

Ligerin, an antiproliferative chlorinated sesquiterpenoid from a marine-derived Penicillium strain.

A new chlorinated sesquiterpenoid analogue of fumagillin, ligerin (1), was isolated from a marine-derived strain of Penicillium, belonging to the subgenus Penicillium, along with the known compounds penicillic acid (2), orcinol, and orsellinic acid. Chemical structures were established by an interpretation of spectroscopic data including IR, UV, and HRESIMS, together with analyses of 1D and 2D NMR spectra and X-ray analysis for the determination of the absolute configuration. Ligerin (1) displayed strong inhibitory activity against an osteosarcoma cell line. This is the first report of the isolation of a fumagillin analogue from a marine-derived Penicillium strain.

Treatment of bone metastasis in prostate cancer: efficacy of a novel polybisphosphonate.

AIM: To investigate the in vivo efficacy of a novel polybisphosphonate (ODX) in the treatment of bone metastasis from prostate cancer. MATERIAL AND METHODS: A rat prostatic carcinoma model was used. Forty-two rats (21 control, 21 treatment) had induction of bone lesions through injection of AT6.1 cells into the distal medullar cavity of long bones (right femur). At day 21 post injection, radiographs were taken and tumor score (severity of lesions, 0-4) and tumor incidence (score >0) were determined. Treatment started at day 23 and lasted until day 49 (four i.v. administrations of ODX during four weeks). RESULTS: ODX reduced the severity of the lesions compared to the control group. Forty-seven percent of the treated rats had regression of their lesions at the study end, including four rats showing disappearance of the lesions i.e. score 0. Osteocondensation at the growth plate was only observed in the treatment group, indicating osteoclast inhibition. CONCLUSION: In spite of a relatively short treatment period with only four administrations, ODX showed significant efficacy (p=0.0023), with inhibition of tumor progression and osteolysis. The results are encouraging, confirming previous in vitro studies. Clinical research is pending on patients with bone metastasis from castration-resistant prostate cancer.