Melphalan-flufenamide is cytotoxic and potentiates treatment with chemotherapy and the Src inhibitor dasatinib in urothelial carcinoma

Pharmacokinetics and Metabolism of Melflufen, an Alkylating Peptide-Drug Conjugate, in Patients with Relapsed Refractory Multiple Myeloma

Melphalan flufenamide (melflufen) is a novel lipophilic peptide-drug conjugate recently approved in the European Union and the United Kingdom for the treatment of relapsed refractory multiple myeloma. Melflufen rapidly crosses the cell membrane, and inside tumor cells, melflufen utilizes peptidases and esterases to release entrapped hydrophilic metabolites with alkylating activity. In vitro, in whole blood, melflufen was rapidly distributed into blood cells and quickly converted to its main metabolite melphalan, with maximum cellular concentrations of noncovalently bound melflufen and melphalan after 1 and 6 minutes, respectively. Melphalan outflow from blood cells was slow, with peak concentrations in plasma after 25 minutes. The pharmacokinetics of melflufen was best described by a 2-compartment model. Following a 30-minutes intravenous infusion of 40 mg in 27 patients with relapsed refactory multiple myeloma, mean half-life in the α phase of the curve was 1.24 minutes, half-life in the β phase of the curve 26.7 minutes, and clearance 13.4 L/min. Desethyl-melflufen exposure was below 20% compared to melflufen. Based on population analysis (298 patients with relapsed refactory multiple myeloma), the melphalan pharmacokinetics were well characterized by a 3-compartment model with melflufen dosing into a peripheral compartment, assuming instantaneous distribution of melflufen into cells and subsequent rapid metabolism to melphalan. Mean clearance and central and deep peripheral volumes of distribution were 22.4 L/h, 2.70 L, and 51.3 L, respectively. Clearance increased and maximum concentration decreased with increasing body weight and estimated glomerular filtration rate. In conclusion, melflufen administration differs from melphalan administration by a more rapid distribution into cells, which, in conjunction with a rapid intracellular metabolism, allows for higher maximum concentrations of alkylating agents, and by a more extensive distribution of melphalan to peripheral tissues.

A rapid intracellular enrichment of alkylating payload is essential for melphalan flufenamide potency and mechanism of action

Despite decades of development of treatments and the successful application of targeted therapies for multiple myeloma, clinical challenges remain for patients with relapsed/refractory disease. A drug designed for efficient delivery of an alkylating payload into tumor cells that yields a favorable therapeutic window can be an attractive choice. Herein we describe melphalan flufenamide (melflufen), a drug with a peptide carrier component conjugated to an alkylating payload, and its cellular metabolism. We further underline the fundamental role of enzymatic hydrolysis in the rapid and robust accumulation of alkylating metabolites in cancer cells and their importance for downstream effects. The formed alkylating metabolites were shown to cause DNA damage, both on purified DNA and on chromatin in cells, with both nuclear and mitochondrial DNA affected in the latter. Furthermore, the rapid intracellular enrichment of alkylating metabolites is shown to be essential for the rapid kinetics of the downstream intracellular effects such as DNA damage signaling and induction of apoptosis. To evaluate the importance of enzymatic hydrolysis for melflufen's efficacy, all four stereoisomers of the compound were studied in a systematic approach and shown to have a different pattern of metabolism. In comparison with melflufen, stereoisomers lacking intracellular accumulation of alkylating payloads showed cytotoxic activity only at significantly higher concentration, slower DNA damage kinetics, and different mechanisms of action to reach cellular apoptosis.

A Phase I Study of the Non-Receptor Kinase Inhibitor Bosutinib in Combination with Pemetrexed in Patients with Selected Metastatic Solid Tumors

Src is overexpressed in various cancers, including 27% of non-small cell lung cancer NSCLC, and is correlated with poor clinical outcomes. We hypothesize that Src kinase inhibitors, including Bosutinib, may exhibit clinical synergy in combination with the antifolate drug pemetrexed. In this Phase I, dose-escalation, safety, and maximum tolerated dose (MTD)-determining study, 14 patients with advanced metastatic solid tumors that had progressed on "standard of care" chemotherapy were enrolled in a 3 + 3 dose escalation study. Oral Bosutinib was administered once daily beginning on day 1, where the first cohort started at an oral dose of 200 mg daily with pemetrexed 500 mg/m² IV on a three-week schedule. The study's primary objective was to determine the dose-limiting toxicity (DLT), the MTD of Bosutinib in combination with pemetrexed, and the type and frequency of adverse events associated with this treatment. Twelve patients were evaluable for response, including ten patients with adenocarcinoma of the lung, one patient with metastatic adenocarcinoma of the appendix, and one patient with urothelial carcinoma. The median number of Bosutinib and pemetrexed cycles received was 4 (range, 1-4). The MTD of oral Bosutinib in this combination was 300 mg daily. Two patients (17%) had a partial response (PR), and seven patients (58%) showed stable disease (SD) as the best response after the fourth cycle (end of treatment). One patient had disease progression after the second cycle, while three patients had disease progression after the fourth cycle. The two responders and the two patients with the longest stable disease duration or stabilization of disease following progression on multiple systemic therapies demonstrated Src overexpression on immunohistochemical staining of their tumor. The median progression-free survival (PFS) was 6.89 months (95% CI (3.48, 30.85)), and the median overall survival (OS) was 11.7 months (95% CI (3.87, 30.85)). Despite the limitations of this Phase I study, there appears to be potential efficacy of this combination in previously treated patients.

Treatment of Multiple Myeloma and the Role of Melphalan in the Era of Modern Therapies-Current Research and Clinical Approaches

Multiple myeloma (MM) accounts for 10% of all hematological malignancies, and it is the second most common hematological neoplasm for which chemotherapy is an important pharmacological treatment. High dose melphalan followed by autologous stem cell transplantation remains the standard of treatment for transplant-eligible patients with MM. In this review, we describe aspects of the pharmacokinetics and pharmacodynamics of melphalan therapy and related compounds. In addition, we describe the use of melphalan in innovative therapies for the treatment of MM, including the development of drug carriers to reduce systemic toxicity, combination therapy to improve the effectiveness of cancer therapy, and the chemical modification of the melphalan molecule to improve antitumor activity.

Identification of Key Genes and miRNAs in Osteosarcoma Patients with Chemoresistance by Bioinformatics Analysis

Chemoresistance is a significant factor associated with poor outcomes of osteosarcoma patients. The present study aims to identify Chemoresistance-regulated gene signatures and microRNAs (miRNAs) in Gene Expression Omnibus (GEO) database. The results of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) included positive regulation of transcription, DNA-templated, tryptophan metabolism, and the like. Then differentially expressed genes (DEGs) were uploaded to Search Tool for the Retrieval of Interacting Genes (STRING) to construct protein-protein interaction (PPI) networks, and 9 hub genes were screened, such as fucosyltransferase 3 (Lewis blood group) (FUT3) whose expression in chemoresistant samples was high, but with a better prognosis in osteosarcoma patients. Furthermore, the connection between DEGs and differentially expressed miRNAs (DEMs) was explored. GEO2R was utilized to screen out DEGs and DEMs. A total of 668 DEGs and 5 DEMs were extracted from GSE7437 and GSE30934 differentiating samples of poor and good chemotherapy reaction patients. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was used to perform GO and KEGG pathway enrichment analysis to identify potential pathways and functional annotations linked with osteosarcoma chemoresistance. The present study may provide a deeper understanding about regulatory genes of osteosarcoma chemoresistance and identify potential therapeutic targets for osteosarcoma.

Designed Tetrapeptide Interacts with Tubulin and Microtubule

Microtubules regulate eukaryotic cell functions, which have tremendous implication in tumor progression. Thus, the design of novel approaches for controlling microtubule function is extremely important. In this manuscript, a novel tetrapeptide Ser-Leu-Arg-Pro (SLRP) has been designed and synthesized from a small peptide library consisting of 14 tetrapeptides, which perturbs microtubule function through interaction in the "anchor region". We have studied the role of peptides on microtubule function on a chemically functionalized 2D platform. Interestingly, we have found that SLRP binds with tubulin and inhibits the kinesin-driven microtubule motility on a kinesin-immobilized chemically functionalized 2D platform. Further, this peptide modulator interacts with intracellular tubulin/microtubule and depolymerizes the microtubule networks. These interesting findings of perturbation of microtubule function both on engineered platforms and inside the cell by this small peptide modulator inspired us to study the effect of this tetrapeptide on cancer cell proliferation. We found that the novel tetrapeptide modulator causes moderate cytotoxicity to the human breast cancer cell (MCF-7 cell), induces the apoptotic death of MCF-7 cell, and activates the tumor suppressor proteins p53 and cyclin-dependent kinase inhibitor 1 (p21). To the best of our knowledge, this is the shortest peptide discovered, which perturbs microtubule function both on an engineered 2D platform and inside the cell.

Melflufen - a peptidase-potentiated alkylating agent in clinical trials

Aminopeptidases like aminopeptidase N (APN, also known as CD13) play an important role not only in normal cellular functioning but also in the development of cancer, including processes like tumor cell invasion, differentiation, proliferation, apoptosis, motility, and angiogenesis. An increased expression of APN has been described in several types of human malignancies, especially those characterized by fast-growing and aggressive phenotypes, suggesting APN as a potential therapeutic target.

Melphalan flufenamide ethyl ester (melflufen, previously denoted J1) is a peptidase-potentiated alkylating agent. Melflufen readily penetrates membranes and an equilibrium is rapidly achieved, followed by enzymatic cleavage in aminopeptidase positive cells, which results in trapping of less lipophilic metabolites. This targeting effect results in very high intracellular concentrations of its metabolite melphalan and subsequent apoptotic cell death. This results in a potency increase (melflufen vs melphalan) ranging from 10- to several 100-fold in different in vitro models. Melflufen triggers a rapid, robust, and an irreversible DNA damage which may account for its ability to overcome melphalan-resistance in multiple myeloma cells. Furthermore, anti-angiogenic properties of melflufen have been described.

Consequently, it is hypothesized that melflufen could provide better efficacy but no more toxicity than what is achieved with melphalan, an assumption so far supported by experiences from hollow fiber and xenograft studies in rodents as well as by clinical data from patients with solid tumors and multiple myeloma. This review summarizes the current preclinical and clinical knowledge of melflufen.

Dasatinib synergises with irinotecan to suppress hepatocellular carcinoma via inhibiting the protein synthesis of PLK1

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common types of malignant tumour and has poor prognosis. Currently, systematic chemotherapy is the only approach to prolong survival. Thus the development of new treatment regimens is urgently needed to improve the therapeutic efficacy. Our study intended to assess the combination of dasatinib and irinotecan against HCC and made an effort to develop a potential medical choice for advanced HCC patients.

METHODS

We used SRB colorimetric assay and clonogenic assay to assess antitumour effect in vitro and HCC xenograft model to assess antitumour effect in vivo. We applied flow cytometry and western blotting to explore the mechanism of the combined therapy. Knockdown and overexpression of PLK1 are also applied for validation.

RESULTS

We confirmed that dasatinib has synergistic effect with irinotecan (or SN38) on HCC both in vitro and in vivo. The effect is due to arisen apoptosis rate of HCC cells that is accompanied by mitochondria dysfunction. The enhanced antitumour efficacy of SN38 could be explained by additional inhibition of PLK1, which is triggered by dasatinib. Unlike existed PLK1 inhibitors, dasatinib does not inhibit PLK1 activity in a direct way. Instead, we found that dasatinib reduces PLK1 level by interfering with its protein synthesis progress. We validated that this kind of downregulation of PLK1 level has a key role in the synergistic effect of the two agents.

CONCLUSIONS

Dasatinib is able to reinforce the anti-HCC efficacy of irinotecan/SN38 by downregulation of PLK1 synthesis. The combination of the two agents might be a potential medical choice for HCC therapy.

Melphalan-flufenamide is cytotoxic and potentiates treatment with chemotherapy and the Src inhibitor dasatinib in urothelial carcinoma

BACKGROUND

Chemotherapy options in advanced urothelial carcinoma (UC) remain limited. Here we evaluated the peptide-based alkylating agent melphalan-flufenamide (mel-flufen) for UC.

METHODS

UC cell lines J82, RT4, TCCsup and 5637 were treated with mel-flufen, alone or combined with cisplatin, gemcitabine, dasatinib or bestatin. Cell viability (MTT assay), intracellular drug accumulation (liquid chromatography) apoptosis induction (apoptotic cell nuclei morphology, western blot analysis of PARP-1/caspase-9 cleavage and Bak/Bax activation) were evaluated. Kinome alterations were characterized by PathScan array and phospho-Src validated by western blotting. Aminopeptidase N (ANPEP) expression was evaluated in UC clinical specimens in relation to patient outcome.

RESULTS

In J82, RT4, TCCsup and 5637 UC cells, mel-flufen amplified the intracellular loading of melphalan in part via aminopeptidase N (ANPEP), resulting in increased cytotoxicity compared to melphalan alone. Mel-flufen induced apoptosis seen as activation of Bak/Bax, cleavage of caspase-9/PARP-1 and induction of apoptotic cell nuclei morphology. Combining mel-flufen with cisplatin or gemcitabine in J82 cells resulted in additive cytotoxic effects and for gemcitabine also increased apoptosis induction. Profiling of mel-flufen-induced kinome alterations in J82 cells revealed that mel-flufen alone did not inhibit Src phosphorylation. Accordingly, the Src inhibitor dasatinib sensitized for mel-flufen cytotoxicity. Immunohistochemical analysis of the putative mel-flufen biomarker ANPEP demonstrated prominent expression levels in tumours from 82 of 83 cystectomy patients. Significantly longer median overall survival was found in patients with high ANPEP expression (P = 0.02).

CONCLUSION

Mel-flufen alone or in combination with cisplatin, gemcitabine or Src inhibition holds promise as a novel treatment for UC.