Helix Biopharma (Canada)

IntroductionTumor acidity is emerging as a hallmark of cancer and carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) expression is frequently increased in acidic tumors. L-DOS47, a novel antibody-drug conjugate (ADC), consists of jack bean urease cross-linked to anti-CEACAM6 nanobodies. L-DOS47 is thus both targeted to CEACAM6-expressing tumors and designed to improve tumor control by neutralizing the acidic tumor microenvironment (TME) through ammonia and bicarbonate production from local urea.MethodsThis open-label, non-randomized study evaluated safety and tolerability of L-DOS47 in Stage IIIB/IV non-small cell lung cancer (NSCLC) patients. The Phase I 3 + 3 dose escalation aimed to determine the maximum tolerated dose (MTD) of L-DOS47 administered once/week over 14 days followed by seven days rest. Phase II explored twice-weekly dosing.Results55/90 patients enrolled in Phase I received L-DOS47 up to 13.55 μg/kg. Although one dose-limiting toxicity (DLT) occurred in a patient at 5.76 μg/kg, MTD was not reached. Common treatment-emergent adverse events (TEAEs), reported by 38% of patients, were respiratory/thoracic/mediastinal disorders including dyspnea. No complete (CR) or partial responses (PR) were observed in Phase I or Phase II, despite the latter’s intensified dosing regimen; however, Phase I post-hoc exploratory analyses found that progression-free survival (PFS) was significantly extended at doses ≥5.76 μg/kg (P=0.0203). Anti-L-DOS47 antibody (ADA) titers were not associated with AE or shorter PFS. Immunohistochemistry (IHC) screening of an unrelated cohort revealed high CEACAM6 expression in 45.2% NSCLC cases.ConclusionsL-DOS47 monotherapy was well tolerated at doses up to 13.55 μg/kg. No CRs or PRs were observed but extended PFS was associated with higher doses. Screening for CEACAM6 expression may select patients who are more likely to derive benefit from L-DOS47.Clinical Trial Registrationhttps://www.clinicaltrialsregister.eu/ctr-search/search; EudraCT Identifier: 2010-020729-42 (May 6, 2010).

Abstract Many solid human tumors generate an acidic and hypoxic microenvironment as a result of altered metabolic pathways and aberrant tumor vasculature. In certain tumors, the chronic exposure to acidic extracellular conditions has been reported to promote invasiveness and metastatic behaviour. In addition, the lower pH may promote resistance to weakly basic chemotherapeutic agents by altering their partitioning coefficient between the extracellular and intracellular compartments. L-DOS47, an immunoconjugate cancer therapeutic, has been developed to target this unique tumor microenvironment. L-DOS47 is a conjugate of a lung adenocarcinoma specific single domain antibody and a urease enzyme. The antibody serves as a targeting agent to deliver the enzyme to the affected site while the urease enzyme coverts urea, an abundant metabolite, into ammonia and generates a local pH increase. The combined effect of ammonia toxicity and pH increase is cytotoxic to cancer cells as shown both in culture and in xenograft models. In vitro experiments showed that L-DOS47 also dramatically potentiated the cytotoxicity of a number of chemotherapeutics. Imaging studies using A549 xenografts and labelled L-DOS47 applied intravenously showed that the drug molecule preferentially accumulated and persisted at the tumor site. L-DOS47 has been studied in a number of tissue-cross reactivity studies to identify suitable animal species for toxicological studies. Cryosections of normal human, cynomolgus monkey, Sprague-Dawley rat, and CD-1 mouse tissues were compared. L-DOS47 produced specific staining to control material (BxPC-3 cells) and those tissues that are known to express CEACAM6 - an antigen for L-DOS47. Both cytoplasmic and membrane bound staining were observed. Results of these studies suggest that the primate and both rodent species are suitable for animal toxicological studies. Pivotal GLP compliant animal toxicological studies in cynomologus monkey and rat together with several non-GLP pilot animal studies were done. In the primate GLP study, L-DOS47 (0, 17, 26, and 35 μg/kg) was administered by IV infusion on Days 1, 8, 15 and 22, followed by a 28-day recovery period. Main study animals were sacrificed on Day 25 and recovery animals on Day 50. Standard toxicology parameters were evaluated. In addition, toxicokinetics, cytokine stimulation and immunogenicity were also evaluated. A separate cardiovascular safety pharmacology study was also conducted. No treatment related clinical signs were observed for the animals treated with 17 or 26μg/kg of L-DOS47. Adverse signs were observed in some but not all of the high dose (35 μg/kg) treated animals. Based on adverse clinical signs observed at 35μg/kg, the NOAEL was determined to be 26 μg/kg/day in this study. Currently L-DOS47 is approved for phase I/II studies in Europe and the U.S.A. Patient enrollment has begun in Poland and first patient has been dosed. Citation Format: Heman Chao, Baomin Tian, Kim Gaspar, John Docherty, Wah Wong. Development of an alkalizing antibody-enzyme conjugate for NSCLC treatment that is in Phase I clinical testing. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2851. doi:10.1158/1538-7445.AM2013-2851

l-Tryptophan decarboxylase (TDC) (EC 4.2.1.27) enzyme activity was induced in cell suspension cultures of Catharanthus roseus after treatment with a Pythium aphanidermatum elicitor preparation. The enzyme was extracted from lyophilized cells containing high levels of TDC and the protein was purified to homogeneity. The pure protein was used to produce highly specific polyclonal antibodies, and an enzyme-linked immunosorbent assay (ELISA) was developed to quantitate the level of TDC antigen during seedling development and in leaves of the mature plant. Western immunoblotting of proteins after SDS-PAGE with anti-TDC antibodies detected several immunoreactive proteins (40, 44, 54.8, 55, and 67 kilodaltons) which appeared at different stages during seedling development and in leaves of the mature plant. The major 54.8 and 55 kilodalton antigenic proteins in immunoblots appeared transiently between days 1 to 5 and 5 to 8 of seedling development, respectively. The 54.8 kilodalton protein was devoid of TDC enzyme activity, whereas the appearance of the 55 kilodalton protein coincided with the appearance of this decarboxylase activity. The minor immunoreactive proteins (40, 44, and 67 kilodaltons) appeared after day 5 of seedling development and in older leaves of the mature plant, and their relationship, if any, to TDC is presently unknown. Results suggest that the synthesis and degradation of TDC protein is highly regulated in Catharanthus roseus and that this regulation follows a preset developmental program.