Combinatorial Biosynthesis of 3-O-Carbamoylmaytansinol by Rational Engineering of the Tailoring Steps of Ansamitocins.

Currently, most maytansine-containing antibody-drug conjugates (ADCs) in clinical trials are prepared with DM1 or DM4, which in turn is synthesized mainly from ansamitocin P-3 (AP-3), a bacterial maytansinoid, isolated from Actinosynnema pretiosum. However, due to the high self-toxicity of AP-3 to A. pretiosum, the yield of AP-3 has been difficult to improve. Herein, a new maytansinoid with much lower self-toxicity to A. pretiosum, 3-O-carbamoylmaytansinol (CAM, 3), was designed and generated by introducing the 3-O-carbamoyltransferase gene asc21b together with the N-methyltransferase genes from exogenous maytansinoid gene clusters into the 3-O-acyltransferase gene (asm19) deleted mutant HGF052. Meanwhile, two new shunt products, 20-O-demethyl-19-dechloro-N-demethyl-4,5-desepoxy-CAM (4) and 20-O-demethyl-N-demethyl-4,5-desepoxy-CAM (5) were identified from the recombinant strain. Furthermore, by screening of liquid fermentation media, overexpression of bottleneck tailoring enzymes and the pathway-specific activator, the titer of CAM reached 498 mg/L in the engineered strain. Since the 3-O-carbamoyl group of CAM can be removed by chemical cleavage as AP-3 to produce maytansinol, our work suggests that CAM may be a promising alternative to AP-3 in the future development of ADCs.

A phase I study of Mirvetuximab Soravtansine and gemcitabine in patients with FRα-positive recurrent ovarian, primary peritoneal, fallopian tube, or endometrial cancer, or triple negative breast cancer.

OBJECTIVE: Platinum-resistant epithelial ovarian cancer (EOC), recurrent endometrial cancer (EC), and triple negative breast cancer (TNBC) are difficult to treat after failing standard therapies. This phase I study evaluated mirvetuximab soravtansine (MIRV) and gemcitabine in patients with recurrent FRα-positive EOC, EC, or TNBC to determine the maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D) (primary endpoint). METHODS: FRα-positive patients with platinum-resistant EOC, EC, or TNBC with ≤4 prior chemotherapy regimens (2 for EC) were enrolled. FRα expression requirement varied among eligible tumors and changed during the study. RESULTS: Twenty patients were enrolled; 17 were evaluable for DLT. Half the patients received ≥3 prior chemotherapy lines. Most EOC and EC patients (78%) were medium (50-74%) or high(75-100%) FRα expressors. TNBC patients were low (25-49%) FRα expressors. The MTD/RP2D was MIRV 6 mg/kg AIBW D1 and gemcitabine 800 mg/m2 IV, D1 and D8, every 21 days (Dose Level [DL] 3), where 5/7 patients demonstrated a partial response (PR) as their best response, including 2 confirmed ovarian responses whose time-to-progression and duration of response were 7.9/5.4 and 8.0/5.7 months respectively. Most common treatment-related adverse events at MTD were anemia and neutropenia (3/7 each, 43%), diarrhea, hypophosphatemia, thrombocytopenia, and leukopenia (2/7 each, 29%). DLTs were thrombocytopenia (DL1), oral mucositis (DL4) and diarrhea (DL4). Nine of 20 patients (45%; 95% CI: 21.1-68.9%) achieved PR as their best response, with 3/20 patients or 15% (95%CI, 0-32.1%) confirmed PR. CONCLUSION: MIRV and gemcitabine demonstrate promising activity in platinum resistant EOC at RP2D, but frequent hematologic toxicities.

Population pharmacokinetics of mirvetuximab soravtansine in patients with folate receptor-α positive ovarian cancer: The antibody-drug conjugate, payload and metabolite.

AIMS: Mirvetuximab soravtansine is a first-in-class antibody-drug conjugate recently approved for the treatment of folate receptor-α positive ovarian cancer. The aim of this study was to develop a population pharmacokinetic model to describe the concentration-time profiles of mirvetuximab soravtansine, the payload (DM4) and a metabolite (S-methyl-DM4). METHODS: Mirvetuximab soravtansine was administered intravenously from 0.15 to 7 mg/kg to 543 patients with predominantly platinum-resistant ovarian cancer in 3 clinical studies, and the plasma drug concentrations were analysed using a nonlinear mixed-effects modelling approach. Stepwise covariate modelling was performed to identify covariates. RESULTS: We developed a semi-mechanistic population pharmacokinetic model that included linear and nonlinear routes for the elimination of mirvetuximab soravtansine and a target compartment for the formation and disposition of the payload and metabolite in tumour cells. The clearance and volume of the central compartment were 0.0153 L/h and 2.63 L for mirvetuximab soravtansine, 8.83 L/h and 3.67 L for DM4, and 2.04 L/h and 6.3 L for S-methyl-DM4, respectively. Body weight, serum albumin and age were identified as statistically significant covariates. Exposures in patients with renal or hepatic impairment and who used concomitant cytochrome P450 (CYP) 3A4 inhibitors were estimated. CONCLUSION: There is no need for dose adjustment due to covariate effects for mirvetuximab soravtansine administered at the recommended dose of 6 mg/kg based on adjusted ideal body weight. Dose adjustment is not required for patients with mild or moderate renal impairment, mild hepatic impairment, or when concomitant weak and moderate CYP3A4 inhibitors are used.

Mirvetuximab soravtansine in ovarian cancer therapy: expert opinion on pharmacological considerations.

ImmunoGen developed mirvetuximab soravtansine as an antibody-drug conjugate comprising of a humanized anti-folate receptor-α (FRα) monoclonal antibody of IgG1k subtype, a cleavable linker, and a cytotoxic payload, DM4. Mirvetuximab soravtansine was granted accelerated approval by the US FDA on November 14, 2022, for the treatment of adult patients with FRα positive, platinum-resistant epithelial ovarian, fallopian tube or primary peritoneal cancer who have received 1-3 prior systemic treatment regimens. The approval of mirvetuximab soravtansine represents a breakthrough for addressing the unmet medical needs of ovarian cancer, especially for up to 80% of patients who relapse and become resistant to platinum-based chemotherapy, resulting in poor prognosis and limited treatment options. However, it is my impression that addressing several pharmacological factors could improve the safety and efficacy of mirvetuximab soravtansine. This article summarizes the current pharmacological profile of mirvetuximab soravtansine and provides an expert opinion on pharmacological strategies for optimizing its safety and efficacy profile for the treatment of platinum-resistant ovarian cancer.

Efficacy and safety of mirvetuximab soravtansine in recurrent ovarian cancer with FRa positive expression: A systematic review and meta-analysis.

OBJECTIVE: To evaluate the efficacy and safety of mirvetuximab soravtansine in treating recurrent ovarian cancer with folate receptor alpha (FRa) expression. METHODS: A comprehensive search was conducted on online databases, including PubMed, Cochrane Library, and EMBASE, to identify relevant literature about the efficacy and safety of mirvetuximab soravtansine in recurrent ovarian cancer with FRa-positive expression. The keywords were the following: recurrent ovarian cancer, mirvetuximab soravtansine, FRa, and antibody-drug conjugate. Furthermore, studies that satisfied the necessary qualifications were carefully evaluated for further meta-analysis. RESULTS: This meta-analysis involved the examination of seven trials with a total of 631 patients. According to the pooled data, the objective response rate (ORR) was 36% (95%CI: 27%-45%). Similarly, the disease control rate (DCR) was 88% (95% CI: 84-91%). Furthermore, the median progression-free survival (PFS) was determined to be 6.1 months (95% CI: 4.27-7.47). The overall response rate and PFS for platinum-resistant ovarian cancer were found to be 29% (95% CI: 25-32%) and 6.26 months (95% CI: 4.67-7.85), respectively. The most often observed adverse events (AEs) in patients with recurrent ovarian cancer (OC) receiving mirvetuximab soravtansine were blurred vision (all grades: 45%, Grade III: 2%), nausea (all grades: 42%, Grade III: 1%), and diarrhea (all grades: 42%, Grade III: 2%). These AEs were specifically associated with the safety profile of mirvetuximab soravtansine in this patient population. CONCLUSION: The efficacy of mirvetuximab soravtansine in treating recurrent ovarian cancer with FRa-positive expression is satisfactory, and the safety is tolerable.

Mirvetuximab soravtansine-gynx: first antibody/antigen-drug conjugate (ADC) in advanced or recurrent ovarian cancer.

Mirvetuximab soravtansine-gynx (MIRV) is a conjugate of a folate receptor alpha (FRα)-directed antibody and the maytansinoid microtubule inhibitor, DM4. Accumulating pre-clinical and clinical data supported the safety and anti-tumor activity of MIRV in tumors expressing FRα. In 2017, a phase I expansion study reported the first experience of MIRV in FRα-positive platinum-resistant ovarian cancer with promising results. However, the phase III FORWARD I study failed to demonstrate a significant benefit of MIRV in FRα-positive tumors. On the basis of the data reported from this latter study, MIRV was then explored in the FRα-high population only and using a different folate receptor assay. The phase II SORAYA trial supported the adoption of MIRV in this setting. Hence, the US Food and Drug Administration granted accelerated approval of MIRV for patients with FRα-positive platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer who have received 1-3 prior systemic treatment regimens. Moreover, the results of the MIRASOL trial showed a significant reduction in the risk of tumor progression or death among patients treated with MIRV versus chemotherapy. VENTANA FOLR1 (FOLR-2.1) was approved as a companion diagnostic test to identify FRα patients. MIRV appears to be a significant asset in managing advanced or recurrent ovarian cancer. Further trials are needed to confirm these promising results, even in the neoadjuvant, adjuvant, and maintenance settings.

Mirvetuximab Soravtansine in FRα-Positive, Platinum-Resistant Ovarian Cancer.

BACKGROUND: Mirvetuximab soravtansine-gynx (MIRV), a first-in-class antibody-drug conjugate targeting folate receptor α (FRα), is approved for the treatment of platinum-resistant ovarian cancer in the United States. METHODS: We conducted a phase 3, global, confirmatory, open-label, randomized, controlled trial to compare the efficacy and safety of MIRV with the investigator's choice of chemotherapy in the treatment of platinum-resistant, high-grade serous ovarian cancer. Participants who had previously received one to three lines of therapy and had high FRα tumor expression (≥75% of cells with ≥2+ staining intensity) were randomly assigned in a 1:1 ratio to receive MIRV (6 mg per kilogram of adjusted ideal body weight every 3 weeks) or chemotherapy (paclitaxel, pegylated liposomal doxorubicin, or topotecan). The primary end point was investigator-assessed progression-free survival; key secondary analytic end points included objective response, overall survival, and participant-reported outcomes. RESULTS: A total of 453 participants underwent randomization; 227 were assigned to the MIRV group and 226 to the chemotherapy group. The median progression-free survival was 5.62 months (95% confidence interval [CI], 4.34 to 5.95) with MIRV and 3.98 months (95% CI, 2.86 to 4.47) with chemotherapy (P<0.001). An objective response occurred in 42.3% of the participants in the MIRV group and in 15.9% of those in the chemotherapy group (odds ratio, 3.81; 95% CI, 2.44 to 5.94; P<0.001). Overall survival was significantly longer with MIRV than with chemotherapy (median, 16.46 months vs. 12.75 months; hazard ratio for death, 0.67; 95% CI, 0.50 to 0.89; P = 0.005). During the treatment period, fewer adverse events of grade 3 or higher occurred with MIRV than with chemotherapy (41.7% vs. 54.1%), as did serious adverse events of any grade (23.9% vs. 32.9%) and events leading to discontinuation (9.2% vs. 15.9%). CONCLUSIONS: Among participants with platinum-resistant, FRα-positive ovarian cancer, treatment with MIRV showed a significant benefit over chemotherapy with respect to progression-free and overall survival and objective response. (Funded by ImmunoGen; MIRASOL ClinicalTrials.gov number, NCT04209855.).

Increased yield of AP-3 by inactivation of asm25 in Actinosynnema pretiosum ssp. auranticum ATCC 31565.

Asamitocins are maytansinoids produced by Actinosynnema pretiosum ssp. auranticum ATCC 31565 (A. pretiosum ATCC 31565), which have a structure similar to that of maytansine, therefore serving as a precursor of maytansine in the development of antibody-drug conjugates (ADCs). Currently, there are more than 20 known derivatives of ansamitocins, among which ansamitocin P-3 (AP-3) exhibits the highest antitumor activity. Despite its importance, the application of AP-3 is restricted by low yield, likely due to a substrate competition mechanism underlying the synthesis pathways of AP-3 and its byproducts. Given that N-demethylansamitocin P-3, the precursor of AP-3, is regulated by asm25 and asm10 to synthesize AGP-3 and AP-3, respectively, asm25 is predicted to be an inhibitory gene for AP-3 production. In this study, we inactivated asm25 in A. pretiosum ATCC 31565 by CRISPR-Cas9-guided gene editing. asm25 depletion resulted in a more than 2-fold increase in AP-3 yield. Surprisingly, the addition of isobutanol further improved AP-3 yield in the asm25 knockout strain by more than 6 times; in contrast, only a 1.53-fold increase was found in the WT strain under the parallel condition. Thus, we uncovered an unknown function of asm25 in AP-3 yield and identified asm25 as a promising target to enhance the large-scale industrial production of AP-3.

Anetumab ravtansine versus vinorelbine in patients with relapsed, mesothelin-positive malignant pleural mesothelioma (ARCS-M): a randomised, open-label phase 2 trial.

BACKGROUND: Few treatment options exist for second-line treatment of malignant pleural mesothelioma. We aimed to assess the antibody-drug conjugate anetumab ravtansine versus vinorelbine in patients with unresectable locally advanced or metastatic disease overexpressing mesothelin who had progressed on first-line platinum-pemetrexed chemotherapy with or without bevacizumab. METHODS: In this phase 2, randomised, open-label study, done at 76 hospitals in 14 countries, we enrolled adults (aged ≥18 years) with unresectable locally advanced or metastatic malignant pleural mesothelioma, an Eastern Cooperative Oncology Group performance status of 0-1, and who had progressed on first-line platinum-pemetrexed chemotherapy with or without bevacizumab. Participants were prospectively screened for mesothelin overexpression (defined as 2+ or 3+ mesothelin membrane staining intensity on at least 30% of viable tumour cells by immunohistochemistry) and were randomly assigned (2:1), using an interactive voice and web response system provided by the sponsor, to receive intravenous anetumab ravtansine (6·5 mg/kg on day 1 of each 21-day cycle) or intravenous vinorelbine (30 mg/m2 once every week) until progression, toxicity, or death. The primary endpoint was progression-free survival according to blinded central radiology review, assessed in the intention-to-treat population, with safety assessed in all participants who received any study treatment. This study is registered with ClinicalTrials.gov, NCT02610140, and is now completed. FINDINGS: Between Dec 3, 2015, and May 31, 2017, 589 patients were enrolled and 248 mesothelin-overexpressing patients were randomly allocated to the two treatment groups (166 patients were randomly assigned to receive anetumab ravtansine and 82 patients were randomly assigned to receive vinorelbine). 105 (63%) of 166 patients treated with anetumab ravtansine (median follow-up 4·0 months [IQR 1·4-5·5]) versus 43 (52%) of 82 patients treated with vinorelbine (3·9 months [1·4-5·4]) had disease progression or died (median progression-free survival 4·3 months [95% CI 4·1-5·2] vs 4·5 months [4·1-5·8]; hazard ratio 1·22 [0·85-1·74]; log-rank p=0·86). The most common grade 3 or worse adverse events were neutropenia (one [1%] of 163 patients for anetumab ravtansine vs 28 [39%] of 72 patients for vinorelbine), pneumonia (seven [4%] vs five [7%]), neutrophil count decrease (two [1%] vs 12 [17%]), and dyspnoea (nine [6%] vs three [4%]). Serious drug-related treatment-emergent adverse events occurred in 12 (7%) patients treated with anetumab ravtansine and 11 (15%) patients treated with vinorelbine. Ten (6%) treatment-emergent deaths occurred with anetumab ravtansine: pneumonia (three [2%]), dyspnoea (two [1%]), sepsis (two [1%]), atrial fibrillation (one [1%]), physical deterioration (one [1%]), hepatic failure (one [1%]), mesothelioma (one [1%]), and renal failure (one [1%]; one patient had 3 events). One (1%) treatment-emergent death occurred in the vinorelbine group (pneumonia). INTERPRETATION: Anetumab ravtansine showed a manageable safety profile and was not superior to vinorelbine. Further studies are needed to define active treatments in relapsed mesothelin-expressing malignant pleural mesothelioma. FUNDING: Bayer Healthcare Pharmaceuticals.

Sensitive LC-MS/MS quantification of unconjugated maytansinoid DM4 and its metabolite S-methyl-DM4 in human plasma.

Aim: To report the development and validation of an LC-MS/MS method for the simultaneous determination of unconjugated payload DM4 and its metabolite S-methyl-DM4 in human plasma. Methodology: A workflow of protein precipitation followed by reduction and solid phase extraction was employed to remove antibody-maytansinoid conjugates from plasma matrix, release DM4 from endogenous conjugates, and generate a clean sample extract for analysis, respectively. Sodium adduct species of both analytes were selected for multiple reaction monitoring to meet the assay sensitivity requirement in liquid chromatography with tandem mass spectrometry. Conclusion: The method was fully validated for a dynamic range of 0.100-50.0 ng/ml for both analytes along with desired stability and acceptable incurred sample reanalysis.

Maytansinol Derivatives: Side Reactions as a Chance for New Tubulin Binders.

Maytansinol is a valuable precursor for the preparation of maytansine derivatives (known as maytansinoids). Inspired by the intriguing structure of the macrocycle and the success in targeted cancer therapy of the derivatives, we explored the maytansinol acylation reaction. As a result, we were able to obtain a series of derivatives with novel modifications of the maytansine scaffold. We characterized these molecules by docking studies, by a comprehensive biochemical evaluation, and by determination of their crystal structures in complex with tubulin. The results shed further light on the intriguing chemical behavior of maytansinoids and confirm the relevance of this peculiar scaffold in the scenario of tubulin binders.

Exploiting mesothelin in thymic carcinoma as a drug delivery target for anetumab ravtansine.

BACKGROUND: Thymic epithelial tumours (TETs) are rare tumours comprised of thymomas and thymic carcinoma. Novel therapies are needed, especially in thymic carcinoma where the 5-year survival rate hovers at 30%. Mesothelin (MSLN), a surface glycoprotein that is cleaved to produce mature MSLN (mMSLN) and megakaryocyte potentiating factor (MPF), is expressed in limited tissues. However, its expression is present in various cancers, including thymic carcinoma, where it is expressed in 79% of cases. METHODS: We utilised flow cytometry, in vitro cytotoxicity assays, and an in vivo xenograft model in order to demonstrate the ability of the MSLN targeting antibody-drug conjugate (ADC) anetumab ravtansine (ARav) in inhibiting the growth of thymic carcinoma. RESULTS: Thymoma and thymic carcinoma cell lines express MSLN, and anetumab, the antibody moiety of ARav, was capable of binding MSLN expressing thymic carcinoma cells and internalising. ARav was effective at inhibiting the growth of thymic carcinoma cells stably transfected with mMSLN in vitro. In vivo, 15 mg/kg ARav inhibited T1889 xenograft tumour growth, while combining 7.5 mg/kg ARav with 4 mg/kg cisplatin yielded an additive effect on inhibiting tumour growth. CONCLUSIONS: These data demonstrate that anetumab ravtansine inhibits the growth of MSLN positive thymic carcinoma cells in vitro and in vivo.

Prise en charge médicale de la récidive du cancer épithélial de l'ovaire: Medical management of recurrent epithelial ovarian cancer.

The panel of therapeutic options available for medical treatment of relapsed ovarian cancer increased over the last years. In late, platinum-sensitive relapse, standard treatment remains platinum-based polychemotherapy. The choice between bevacizumab added to chemotherapy followed by maintenance and inhibitors of poly-(ADP-riboses) polymerases (PARPi) after response to platinum-based therapy should be discussed, taking into account prior treatment, contraindications, and disease characteristics (biology, symptoms…). The addition of bevacizumab at first platinum-sensitive relapse can be considered if it has not been administered in first line, and it is optional (rechallenge) if previously administered (but without Marketing Authorization in this setting). PARPi are indicated for maintenance therapy after response to platinum-based chemotherapy (whatever the treatment line), regardless of BRCA mutational status, in case of no prior administration. Early relapses are associated with poor prognosis and therapeutic options are more limited. They are treated by monochemotherapy without platinum agents, associated with bevacizumab if not administered previously. Beyond first early relapse, there is no standard and inclusion in a clinical trial should be proposed if possible. Several clinical studies assessing associations of immunotherapy and chemotherapy and/or antiangiogenic drugs and/or targeted therapies (such as PARPi) are ongoing in early or late relapse.

Indatuximab ravtansine plus dexamethasone with lenalidomide or pomalidomide in relapsed or refractory multiple myeloma: a multicentre, phase 1/2a study.

BACKGROUND: Indatuximab ravtansine (BT062) is an antibody-drug conjugate that binds to CD138 and synergistically enhances the antitumor activity of lenalidomide in preclinical models of multiple myeloma. This phase 1/2a study was done to determine the safety, activity, and pharmacokinetics of indatuximab ravtansine in combination with immunomodulatory drugs in patients with relapsed or refractory multiple myeloma. METHODS: This open-label, phase 1/2a study took place at nine hospital sites in the USA. Eligible patients were aged 18 years or older, had relapsed or refractory multiple myeloma, and ECOG performance status or Zubrod score of 2 or below. Patients who received indatuximab ravtansine with lenalidomide and dexamethasone (indatuximab ravtansine plus lenalidomide) had failure of at least one previous therapy. Patients treated with indatuximab ravtansine with pomalidomide and dexamethasone (indatuximab ravtansine plus pomalidomide) had failure of at least two previous therapies (including lenalidomide and bortezomib) and had progressive disease on or within 60 days of completion of their last treatment. In phase 1, patients received indatuximab ravtansine intravenously on days 1, 8, and 15 of each 28-day cycle in escalating dose levels of 80 mg/m2, 100 mg/m2, and 120 mg/m2, with lenalidomide (25 mg; days 1 to 21 every 28 days orally) and dexamethasone (20-40 mg; days 1, 8, 15, and 22 every 28 days). In phase 2, the recommended phase 2 dose of indatuximab ravtansine was given to an expanded cohort of patients in combination with lenalidomide and dexamethasone. The protocol was amended to allow additional patients to be treated with indatuximab ravtansine plus pomalidomide (4 mg; days 1 to 21 every 28 days orally) and dexamethasone, in a more heavily pretreated patient population than in the indatuximab ravtansine plus lenalidomide group. The phase 1 primary endpoint was to determine the dose-limiting toxicities and the maximum tolerated dose (recommended phase 2 dose) of indatuximab ravtansine, and the phase 2 primary endpoint was to describe the objective response rate (ORR; partial response or better) and clinical benefit response (ORR plus minor response). All patients were analysed for safety and all patients with post-treatment response assessments were analysed for activity. This study is registered with ClinicalTrials.gov, number NCT01638936, and is complete. FINDINGS: 64 (86%) of 74 screened patients were enrolled between July 3, 2012, and June 30, 2015. 47 (73%) patients received indatuximab ravtansine plus lenalidomide (median follow-up 24·2 months [IQR 19·9-45·4]) and 17 (27%) received indatuximab ravtansine plus pomalidomide (24·1 months [17·7-36·7]). The maximum tolerated dose of indatuximab ravtansine plus lenalidomide was 100 mg/m2, and defined as the recommended phase 2 dose for indatuximab ravtansine plus pomalidomide. An objective response for indatuximab ravtansine plus lenalidomide was observed in 33 (71·7%) of 46 patients and in 12 (70·6%) of 17 patients in the indatuximab ravtansine plus pomalidomide group. The clinical benefit response for indatuximab ravtansine plus lenalidomide was 85% (39 of 46 patients) and for indatuximab ravtansine plus pomalidomide it was 88% (15 of 17 patients). The most common grade 3-4 adverse events in both groups were neutropenia (14 [22%] of 64 patients), anaemia (10 [16%]), and thrombocytopenia (seven [11%]). Treatment-emergent adverse events (TEAEs) that led to discontinuation occurred in 35 (55%) of the 64 patients. Five (8%) patients with a TEAE had a fatal outcome; none was reported as related to indatuximab ravtansine. INTERPRETATION: Indatuximab ravtansine in combination with immunomodulatory drugs shows preliminary antitumor activity, is tolerated, and could be further evaluated in patients with relapsed or refractory multiple myeloma. FUNDING: Biotest AG.

A Review on Phytochemicals of the Genus Maytenus and Their Bioactive Studies.

The genus Maytenus is a member of the Celastraceae family, of which several species have long been used in traditional medicine. Between 1976 and 2021, nearly 270 new compounds have been isolated and elucidated from the genus Maytenus. Among these, maytansine and its homologues are extremely rare in nature. Owing to its unique skeleton and remarkable bioactivities, maytansine has attracted many synthetic endeavors in order to construct its core structure. In this paper, the current status of the past 45 years of research on Maytenus, with respect to its chemical and biological activities are discussed. The chemical research includes its structural classification into triterpenoids, sesquiterpenes and alkaloids, along with several chemical synthesis methods of maytansine or maytansine fragments. The biological activity research includes activities, such as anti-tumor, anti-bacterial and anti-inflammatory activities, as well as HIV inhibition, which can provide a theoretical basis for the better development and utilization of the Maytenus.

C3 ester side chain plays a pivotal role in the antitumor activity of Maytansinoids.

Maytansinoids, the chemical derivatives of Maytansine, are commonly used as potent cytotoxic payloads in antibody-drug conjugates (ADC). Structure-activity-relationship studies had identified the C3 ester side chain as a critical element for antitumor activity of maytansinoids. The maytansinoids bearing the methyl group at C3 position with D configuration were about 100 to 400-fold less cytotoxic than their corresponding L-epimers toward various cell lines. The detailed mechanism of how chirality affects the anticancer activity remains elusive. In this study, we determined the high-resolution crystal structure of tubulin in complex with maytansinol, L-DM1-SMe and D-DM1-SMe. And we found the carbonyl oxygen atom of the ester moiety and the tail thiomethyl group at C3 side chain of L-DM1-SMe form strong intramolecular interaction with the hydroxyl at position 9 and the benzene ring, respectively, fixing the bioactive conformation and enhancing the binding affinity. Additionally, ligand-based and structure-based virtually screening methods were used to screen the commercially macrocyclic compounds library, and 15 macrocyclic structures were picketed out as putatively new maytansine-site inhibitors. Our study provides a possible strategy for the rational discovery of next-generation maytansine site inhibitors.

In Vitro and In Vivo Comparison of 3,2-HOPO Versus Deferoxamine-Based Chelation of Zirconium-89 to the Antimesothelin Antibody Anetumab.

Introduction: [227Th]Th-3,2-HOPO-MSLN-mAb, a mesothelin (MSLN)-targeted thorium-227 therapeutic conjugate, is currently in phase I clinical trial; however, direct PET imaging using this conjugate is technically challenging. Thus, using the same MSLN antibody, we synthesized 3,2-HOPO and deferoxamine (DFO)-based zirconium-89 antibody conjugates, [89Zr]Zr-3,2-HOPO-MSLN-mAb and [89Zr]Zr-DFO-MSLN-mAb, respectively, and compared them in vitro and in vivo. Methods: [89Zr]Zr-3,2-HOPO-MSLN-mAb and [89Zr]Zr-DFO-MSLN-mAb were evaluated in vitro to determine binding affinity and immunoreactivity in HT29-MSLN and PDX (NCI-Meso16, NCI-Meso21) cells. For both the zirconium-89 conjugates, in vivo studies (biodistribution/imaging) were performed at days 1, 3, and 6, from which tissue uptake was determined. Results: Both the conjugates demonstrated a low nanomolar binding affinity for MSLN and >95% immunoreactivity. In all the three tumor types, biodistribution of [89Zr]Zr-DFO-MSLN-mAb resulted in higher tumor uptake(15.88-28-33%ID/g) at all time points compared with [89Zr]Zr-3,2-HOPO-MSLN-mAb(7-13.07%ID/g). [89Zr]Zr-3,2-HOPO-MSLN-mAb femur uptake was always higher than [89Zr]Zr-DFO-MSLN-mAb, and imaging results concurred with the biodistribution studies. Conclusions: Even though the conjugates exhibited a high binding affinity for MSLN, [89Zr]Zr-DFO-MSLN-mAb showed a higher tumor and lower femur uptake than [89Zr]Zr-3,2-HOPO-MSLN-mAb. Nevertheless, [89Zr]Zr-3,2-HOPO-MSLN-mAb could be used to study organ distribution and lesion uptake with the caveat of detecting MSLN-positive bone lesions. Clinical trial (NCT03507452).

Improved AP-3 production through combined ARTP mutagenesis, fermentation optimization, and subsequent genome shuffling.

Ansamitocin (AP-3) is an ansamycins antibiotic isolated from Actinosynnema pretiosum and demonstrating high anti-tumor activity. To improve AP-3 production, the A. pretiosum ATCC 31565 strain was treated with atmospheric and room temperature plasma (ARTP). Four stable mutants were obtained by ARTP, of which the A. pretiosum L-40 mutant produced 242.9 mg/L AP-3, representing a 22.5% increase compared to the original wild type strain. With seed medium optimization, AP-3 production of mutant L-40 reached 307.8 mg/L; qRT-PCR analysis revealed that AP-3 biosynthesis-related gene expression was significantly up-regulated under optimized conditions. To further improve the AP-3 production, genome shuffling (GS) technology was used on the four A. pretiosum mutants by ARTP. After three rounds of GS combined with high-throughput screening, the genetically stable recombinant strain G3-96 was obtained. The production of AP-3 in the G3-96 strain was 410.1 mg/L in shake flask cultures, which was 44.5% higher than the L-40 production from the parental strain, and AP-3 was increased by 93.8% compared to the wild-type A. pretiosum. These results suggest that the combination of mutagenesis, seed medium optimization, and GS technology can effectively improve the AP-3 production capacity of A. pretiosum and provide an enabling methodology for AP-3 industrial production.