Purpose: Taxanes are important chemotherapeutic agents with proven efficacy in human cancers, but their use is limited by resistance development. We report here the preclinical characteristics of cabazitaxel (XRP6258), a semisynthetic taxane developed to overcome taxane resistance.Experimental Design: Cabazitaxel effects on purified tubulin and on taxane-sensitive or chemotherapyresistant tumor cells were evaluated in vitro. Antitumor activity and pharmacokinetics of intravenously administered cabazitaxel were assessed in tumor-bearing mice.Results: In vitro, cabazitaxel stabilized microtubules as effectively as docetaxel but was 10-fold more potent than docetaxel in chemotherapy-resistant tumor cells (IC 50 ranges: cabazitaxel, 0.013-0.414 mmol/L; docetaxel, 0.17-4.01 mmol/L). The active concentrations of cabazitaxel in these cell lines were achieved easily and maintained for up to 96 hours in the tumors of mice bearing MA16/C tumors treated with cabazitaxel at 40 mg/kg. Cabazitaxel exhibited antitumor efficacy in a broad spectrum of murine and human tumors (melanoma B16, colon C51, C38, HCT 116, and HT-29, mammary MA17/A and MA16/C, pancreas P03 and MIA PaCa-2, prostate DU 145, lung A549 and NCI-H460, gastric N87, head and neck SR475, and kidney Caki-1). Of particular note, cabazitaxel was active in tumors poorly sensitive or innately resistant to docetaxel (Lewis lung, pancreas P02, colon HCT-8, gastric GXF-209, mammary UISO BCA-1) or with acquired docetaxel resistance (melanoma B16/TXT).Conclusions: Cabazitaxel is as active as docetaxel in docetaxel-sensitive tumor models but is more potent than docetaxel in tumor models with innate or acquired resistance to taxanes and other chemotherapies. These studies were the basis for subsequent clinical evaluation.

Antibody-drug conjugates (ADCs) consist of cytotoxic drugs covalently linked to monoclonal antibodies directed to antigens differentially overexpressed in tumor cells. These loaded antibodies are expected to selectively deliver lethal cargoes to tumor cells and provide sustained clinical benefit to pre-selected cancer patients while, at the same time, minimizing systemic toxicity. Although on-target adverse events are not completely avoided and the true efficacy of these innovative agents still requires further clarification, proof-of-concept has already been achieved in clinical settings with immunoconjugates containing calicheamicin, auristatin or maytansine-based cytotoxic payloads. In this present article we review the characteristics of the preceding cytotoxic platforms and their chemical conjugation approaches.

First-generation taxanes have changed the treatment paradigm for a wide variety of cancers, but innate or acquired resistance frequently limits their use. Cabazitaxel is a novel second-generation taxane developed to overcome such resistance. In vitro, cabazitaxel showed similar antiproliferative activity to docetaxel in taxane-sensitive cell lines and markedly greater activity in cell lines resistant to taxanes. In vivo, cabazitaxel demonstrated excellent antitumor activity in a broad spectrum of docetaxel-sensitive tumor xenografts, including a castration-resistant prostate tumor xenograft, HID28, where cabazitaxel exhibited greater efficacy than docetaxel. Importantly, cabazitaxel was also active against tumors with innate or acquired resistance to docetaxel, suggesting therapeutic potential for patients progressing following taxane treatment and those with docetaxel-refractory tumors. In patients with tumors of the central nervous system (CNS), and in patients with pediatric tumors, therapeutic success with first-generation taxanes has been limited. Cabazitaxel demonstrated greater antitumor activity than docetaxel in xenograft models of CNS disease and pediatric tumors, suggesting potential clinical utility in these special patient populations. Based on therapeutic synergism observed in an in vivo tumor model, cabazitaxel is also being investigated clinically in combination with cisplatin. Nonclinical evaluation of the safety of cabazitaxel in a range of animal species showed largely reversible changes in the bone marrow, lymphoid system, gastrointestinal tract, and male reproductive system. Preclinical safety signals of cabazitaxel were consistent with the previously reported safety profiles of paclitaxel and docetaxel. Clinical observations with cabazitaxel were consistent with preclinical results, and cabazitaxel is indicated, in combination with prednisone, for the treatment of patients with hormone-refractory metastatic prostate cancer previously treated with docetaxel. In conclusion, the demonstrated activity of cabazitaxel in tumors with innate or acquired resistance to docetaxel, CNS tumors, and pediatric tumors made this agent a candidate for further clinical evaluation in a broader range of patient populations compared with first-generation taxanes.

A highly stereocontrolled synthesis of ring D/E precursor to reserpine has been developed starting from (-)-quinic acid as a chiral template. The total synthesis of (-)-reserpine is described through the cyclization of an immonium lactam intermediate.

No abstract

Purpose: Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) is a glycoprotein that has limited expression in normal adult tissues, but is overexpressed in carcinomas of the gastrointestinal tract, the genitourinary and respiratory systems, and breast cancer. As such, CEACAM5 is an attractive target for antibody-based therapies designed to selectively deliver cytotoxic drugs to certain epithelial tumors. Here, we describe preclinical data for a novel antibody–drug conjugate (ADC), SAR408701, which consists of an anti-CEACAM5 antibody (SAR408377) coupled to a maytansinoid agent DM4 via a cleavable linker. Experimental Design: The specificity and binding affinity of SAR408701 to human and cynomolgus monkey CEACAM5 were tested in vitro. The cytotoxic activity of SAR408701 was assessed in CEACAM5-expressing tumor cell lines and using patient-derived xenograft mouse models of CEACAM5-positive tumors. Pharmacokinetic-pharmacodynamic and pharmacokinetic-efficacy relationships were established. SAR408701 toxicity was evaluated in cynomolgus monkey. Results: SAR408701 bound selectively to human and cynomolgus monkey CEACAM5 with similar apparent Kd values (0.017 nmol/L and 0.024 nmol/L, respectively). Both in vitro and in vivo evaluations showed that SAR408701 has cytotoxic activity, leading to in vivo efficacy in single and repeated dosing. Single doses of SAR408701 induced significant increases in the tumor expression of phosphorylated histone H3, confirming the tubulin-targeting mechanism of action. The overall toxicity profile of SAR408701 in cynomolgus monkey was similar to that observed after intravenous administration of DM4 alone. Conclusions: On the basis of these preclinical data, the ADC SAR408701 is a promising candidate for development as a potential treatment for patients with CEACAM5-positive tumors.

No abstract

Carcinoembryonic antigen cell adhesion molecule 5, CEACAM5 (CEA, CD66e) is a well known tumor marker, in particular in colorectal carcinomas, where circulating CEA is used to monitor response to chemotherapy. This GPI anchored glycoprotein belongs to the CEA-related cell adhesion molecule (CEACAM) family and shares domains identity to other members, like CEACAM6. CEACAM5 is expressed in non-human primate and also shares identity to different members, making it difficult to find an antibody both selective to human CEACAM5 and cross-reacting solely with monkey CEACAM5. CEACAM5 has been described in the literature as a poorly internalizing surface protein, but interestingly, antibodies with different uptake capacities have been found. CEACAM5 is highly expressed at the surface of tumor cells in several epithelial tumors, including CRC, lung and gastric tumors and displays a limited expression in normal tissue where it is found solely at the luminal surface of columnar absorptive cells. This prompted us to develop an anti-CEACAM5 antibody-drug conjugate (ADC) for the treatment of CEACAM5-positive tumors. We generated multiple anti-CEACAM5 antibodies by immunization of Balb/c mice with recombinant human and monkey CEACAM5 extracellular domain and CEACAM5-positive tumor cells. We selected a highly specific CEACAM5 antibody that cross-reacts with monkey. The Alexa488-labeled anti CEACAM5 antibody internalizes in tumor cells and is processed in lysosomes leading to free Alexa488 molecules. Although the internalization rate was shown to be moderate, the high number of CEACAM5 at the surface of tumor cells allowed to produce a high number of free Alexa488, suggesting that the antibody could be suited for conjugation to a cytotoxic molecule. Indeed, conjugation of the antibody to the cytotoxic maytansinoid, DM4, with the cleavable SPDB linker generated SAR408701, which kills different CEACAM5-positive tumor cells at sub-nM concentration. SAR408701 in vivo efficacy was evaluated in CRC, lung and gastric patient-derived xenografts (PDXs), following a single injection of ADC at low doses (2.5-5 mg/kg). The conjugate was able to elicit strong and specific antitumor efficacy in a number of PDX models representative of the CEACAM5-positive patient population. Repeating the administrations resulted in most cases in a more pronounced antitumor efficacy even at doses that were otherwise marginally active as single dose. SAR408701 was well tolerated in cynomologus monkey and displayed similar toxicity profile as other SPDB-DM4 ADCs. Based on preclinical efficacy data and the absence of target mediated toxicity in monkey, SAR408701 is expected to have anticancer activity with a favorable therapeutic index, warranting its evaluation in patients with CEACAM5-positive tumors. Citation Format: Stéphanie Decary, Pierre-François Berne, Céline Nicolazzi, Anne-Marie Lefebvre, Tarik Dabdoubi, Beatrice Cameron, Catherine Devaud, Catherine Prades, Hervé Bouchard, Alhassan Cassé, Christophe Henry, Céline Amara, Paul Ferrari, Laetitia Maçon, Eric Lacoste, Cécile Combeau, Eric Beys, Souad Naimi, Francis Blanche, Carlos Garcia-Echeverria, Jean-François Mayaux, Véronique Blanc. A novel anti-CEACAM5 maytansinoid-antibody-drug conjugate for the treatment of colorectal, lung and gastric tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1688. doi:10.1158/1538-7445.AM2015-1688