Simple and Rapid LC-MS/MS Methods for Quantifying Catabolites of Antibody-Drug Conjugates with SMCC Linker.

The stability and exposure of toxin-related catabolites in system circulation contributes to the evaluation of the stability, targeted delivery and off-target toxicity for antibody-drug conjugates (ADC) at different stages during drug development. In this study, simple and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods for determination catabolites of Mertansine (DM1), MCC-DM1 and Lys-MCC-DM1 in cynomolgus serum have been developed. The serum samples are processed by protein precipitation. The LC-MS/MS methods are applied on a Phenomenex C8 column (50 × 2.0 mm, 5 µm) with gradient elution with water-formic acid 0.1% (A) and acetonitrile-formic acid 0.1% (B) at a flow rate of 0.5 mL/min. The analytical run time is only 4.0 min and the calibration ranges of the standard curve are 0.500-200 ng/mL for DM1, 1.00-500 ng/mL for MCC-DM1 and 2.00-1000 ng/mL for Lys-MCC-DM1. Intra- and inter-day precision of low, middle and high quality controls was <15%, and accuracy was 99.2-110.9%. The methods were successfully applied to evaluate three catabolites of novel ADCs with N-succinimidyl-4-(N-maleimidomethyl)-cyclohexane-1-carboxylate linker in vitro and in vivo studies.

Identification and Engineering of Post-PKS Modification Bottlenecks for Ansamitocin P-3 Titer Improvement in Actinosynnema pretiosum subsp. pretiosum ATCC 31280.

The type-I polyketide ansamitocin P-3 (AP-3) is a potent antitumor agent. Its production is most likely hampered by the required multiple substrate supplies and complicated post-PKS modifications in Actinosynnema pretiosum subsp. pretiosum ATCC 31280. For titer improvement, gene ansa30, encoding for a glycosyltransferase competing for the N-demethyl-AP-3 (PND-3) intermediate for AP-3 biosynthesis, was initially inactivated. In the mutant NXJ-22, the AP-3 titer was increased by 66% along with an obvious accumulation of PND-3, indicating that the N-methylation is a rate-limiting step. Alternatively, when abundant upstream intermediate 19-chloroproansamitocin was fed into a PKS mutant, 3-O-acylation was further identified along with the N-methylation as the rate-limiting steps. Subsequent overexpression of N-methyltransferase gene asm10 in NXJ-22 resulted in a 93% increase of AP-3 and a corresponding 92% decrease of PND-3. Additional supplementation of L-methionine, the precursor for SAM biosynthesis, substantially decreased the accumulation of PND-3. In parallel, the 3-O-acylation bottleneck was relieved by feeding with L-valine to NXJ-22, resulting in a 126% increase of AP-3. Eventually, a combined asm10 overexpression and supplementation of L-methionine and L-valine resulted in a 5-fold increase of AP-3, from 42 ± 2 mg L-1 to 246 ± 6 mg L-1 , without any noticeable accumulation of PND-3.

Effects of modulation of pentose-phosphate pathway on biosynthesis of ansamitocins in Actinosynnema pretiosum.

Ansamitocins, produced by Actinosynnema pretiosum, are a group of maytansinoid antibiotics that block the assembly of tubulin into functional microtubules. The precursors of ansamitocin biosynthesis are generally derived from the Embden-Meyerhof-Parnas (EMP) pathway and the tricarboxylic acid cycle. In this study, central carbon flux distributions were analyzed by (13)C-based flux analysis to reveal the contribution of individual central carbon metabolism pathways. To direct more carbon flux into ansamitocin biosynthesis, pentose phosphate (PP) pathway only and the combination of PP pathway and Entner-Doudoroff (ED) pathway were weakened, respectively. Ansamitocin P-3 (AP-3) productions by both kinds of pathways weakened mutant strains were significantly enhanced in chemically defined medium. In order to draw metabolic flux to the biosynthesis of ansamitocins more efficiently, heterologous phosphoglucomutase was subsequently overexpressed based on a mutant strain with combinational regulation of PP pathway and ED pathway. More fluxes were successfully directed into the UDP-glucose synthetic pathway and the AP-3 production was further improved in this case, reaching approximately 185mg/L in fermentation medium. It was demonstrated that eliminating the bypass pathways and favoring the precursor synthetic pathway could effectively improve ansamitocin production by A. pretiosum, suggesting a promising role of metabolic strategy in improving secondary metabolite production.

Occurrence and non-detectability of maytansinoids in individual plants of the genera Maytenus and Putterlickia.

Individual plants belonging to different species of the family Celastraceae collected from their natural habitats in South Africa (Putterlickia verrucosa (E. Meyer ex Sonder) Szyszyl., Putterlickia pyracantha (L.) Szyszyl., Putterlickia retrospinosa van Wyk and Mostert) and Brazil (Maytenus ilicifolia Mart. ex Reiss., Maytenus evonymoides Reiss., Maytenus aquifolia Mart.) were investigated for the presence of maytansinoids and of maytansine, an ansamycin of high cytotoxic activity. Maytansinoids were not detectable in plants grown in Brazil. Analysis of plants growing in South Africa, however, showed clearly that maytansinoids were present in some individual plants but were not detectable in others. Molecular biological analysis of a Putterlickia verrucosa cell culture gave no evidence for the presence of the aminohydroxybenzoate synthase gene which is unique to the biosynthesis of aminohydroxybenzoate, a precursor of the ansamycins including maytansinoids. Moreover, this gene was not detectable in DNA extracted from the aerial parts of Putterlickia plants. In contrast, observations indicate that this gene may be present in microbes of the rhizosphere of Putterlickia plants. Our observations are discussed with respect to the possibility that the roots of Putterlickia plants may be associated with microorganisms which are responsible for the biosynthesis of maytansine or maytansinoids.

Ansamitocin analogs from a mutant strain of Nocardia. I. Isolation of the mutant, fermentation and antimicrobial properties.

A mutant having a high ability to produce ansamitocins was derived from a dnacin-producing strain, Nocardia sp. No. C-14482 (N-1001), by treatment with ethidium bromide. Mutant N-1231 produced ansamitocins P-3 and P-4 as major components, but was deficient in its ability to produce dnacins. Strain N-1231 also produced fifteen novel ansamitocin analogs as minor components. These analogs showed no activity against prokaryotic micro-organisms. The results of determining the activity inhibiting cilia regeneration of deciliated Tetrahymena pyriformis suggest that hydroxylation of C15, C26 and the acyl moiety at C3 of ansamitocins may cause marked reduction of their antitubulinic activities whereas demethylation of -NCH3 at C18 slightly affected their activities.

An API LC/MS/MS quantitation method for ansamitocin P-3 (AP3) and its preclinical pharmacokinetics.

Ansamitocin P-3 (AP3) is a potent maytansinoid antitumor agent isolated from microorganisms and mosses. In this study, a highly sensitive and specific electrospray ionization (ESI) liquid chromatography-tandem mass spectrometry (LC/MS/MS) method for quantitation of AP3 was developed and validated. AP3 was extracted from rat plasma along with the internal standard, depsipeptide FK228 (NSC-630176, FR) with ethyl acetate. Components in the extract were separated on a 50mm x 2.1mm Betabasic C 85 microm stainless steel column by isocratic elution with 70% acetonitrile/0.9% formic acid. The liquid flow was passed through a pre-source splitter and 5% of the eluent was introduced into the API source. The components were analyzed in the multiple-reaction-monitoring (MRM) mode as the precursor/product ion pair of m/z 635.2/547.2 for AP3 and of m/z 541.5/424.0 for the internal standard FR. Linear calibration curves were obtained in the range 1-500 ng/mL using 0.2 mL rat plasma. The within-day coefficients of variation (CVs) were 12.9, 6.7, and 5.5% and the between-day CVs were 10.4, 6.5, and 6.4% (all n = 5) at 1, 10, and 200 ng/mL, respectively. A formulation based on normal saline and PEG300 was then developed and Sprague-Dawley male rats were given this formulated drug by i.v. bolus. Plasma drug concentrations were measured by this method and the pharmacokinetics were analyzed by standard techniques. Plasma concentration-time profiles were found to follow a triexponential decline and the terminal phase was nearly flat, suggesting that the drug distributed in deep tissue compartments or organs and then equilibrates slowly with the blood stream.

[Investigating cytostatic substances in tissue of plants Maytenus Molina in in-vitro cultures. II. chromatographic test of extracts from callus of Maytenus wallichiana R. et B]. / Poszukiwanie substancji cytostatycznych w tkankach roslin rodzaju Maytenus Molina w kulturze in vitro. II. Badania chromatograficzne wyciagów z kalusa Maytenus wallichiana R. et B.

Maytenus wallichiana callus tissue was extracted. The extract was fractionated to achieve maytansine containing residue. In none of the fractions maytansine corresponding substance was found. However evaluation by Tetrahymena test indicated strong cytotoxicity (ID50 1.8 micrograms/cm3). Chromatography of biologically active fractions demonstrated the presence of colour chinone methide triterpenes (tingenone).

PK assays for antibody-drug conjugates: case study with ado-trastuzumab emtansine.

BACKGROUND: Antibody-drug conjugates (ADCs) combine the characteristics of large-molecule biologics and small-molecule drugs and are heterogeneous mixtures that can biotransform in vivo, resulting in additional complexity. ADC bioanalytical strategies require novel analytical methods, as well as existing large- and small-molecule methods. Because ADCs in late-stage clinical development are relatively new, regulatory guidelines and standard industry best practices for developing strategies for bioanalytical PK assays are still being established. RESULTS: A PK assay strategy was developed that included comprehensive novel reagent and assay characterization approaches for the ADC ado-trastuzumab emtansine (T-DM1). CONCLUSION: The bioanalytical strategy was successfully applied to the drug development of T-DM1 and ensured that key analytes were accurately measured in support of nonclinical and clinical development.

A reversed-phase high-performance liquid chromatography method for analysis of monoclonal antibody-maytansinoid immunoconjugates.

A reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for detection and quantification of free maytansinoid drug in disulfide-linked conjugates between monoclonal antibodies and the maytansinoid drug DM1 (MAb-DM1). Mobile phases and gradient conditions were optimized for separation of several DM1-related free drug species from MAb-DM1 conjugates. The selectivity, linearity, and reproducibility of the method are reported. Reduction of the disulfide-linked DM1 followed by RP-HPLC allowed estimation of purity of MAb-linked DM1 as well as recovery of L-DM1. The method was also used to estimate drug per MAb ratios, which were consistent with those determined by UV spectroscopy.

Microbiological assays and bioautography of maytansine and its homologues.

A quantitative microbiological assay and a bioautography system with Penicillium avellaneum UC-4376 was developed for the antitumor drugs maytansine, and its homologues, maytanprine and maytanbutine. The susceptibility of the assay is 1.5 mug/ml.