rrx-001 and Multiple-Myeloma

Multiple myeloma is currently incurable, and the incidence rate is increasing year by year worldwide. Although in recent years the combined treatment plan based on proteasome inhibitors and immunomodulatory drugs has greatly improved the treatment effect of multiple myeloma, most patients still relapse and become resistant to current treatments. To solve this problem, scientists are committed to developing drugs with higher specificity, such as iberdomide, which is highly specific to ikaros and aiolos. This review aims to focus on the small molecular agents that are being researched/clinically used for the treatment of multiple myeloma, including the target mechanism, structure-activity relationship and application prospects of small molecular agents.

Topics: Animals; Antineoplastic Agents; Biomarkers, Tumor; Combined Modality Therapy; Deubiquitinating Enzymes; Drug Development; Drug Resistance; Histone Deacetylases; Humans; Ikaros Transcription Factor; Immunomodulating Agents; Models, Molecular; Morpholines; Multiple Myeloma; Phthalimides; Piperidones; Proteasome Inhibitors; Treatment Outcome; Ubiquitin-Protein Ligases

The hypoxic bone marrow (BM) microenvironment confers growth/survival and drug resistance in multiple myeloma (MM) cells. Novel therapies targeting the MM cell in its hypoxic BM milieu may overcome drug resistance. Recent studies led to the development of a novel molecule RRx-001 with hypoxia-selective epigenetic and nitric oxide-donating properties. Here, we demonstrate that RRx-001 decreases the viability of MM cell lines and primary patient cells, as well as overcomes drug resistance. RRx-001 inhibits MM cell growth in the presence of BM stromal cells. RRx-001-induced apoptosis is associated with: (i) activation of caspases; (ii) release of ROS and nitrogen species; (iii) induction of DNA damage via ATM/γ-H2AX; and (iv) decrease in DNA methyltransferase (DNMT) and global methylation. RNA interference study shows a predominant role of DNMT1 in MM cell survival versus DNMT3a or DNMT3b. The deubiquitylating enzyme USP7 stimulates DNMT1 activity, and conversely, USP7-siRNA reduced DNMT1 activity and decreased MM cell viability. RRx-001 plus USP7 inhibitor P5091 triggered synergistic anti-MM activity. MM xenograft studies show that RRx-001 is well tolerated, inhibits tumor growth and enhances survival. Combining RRx-001 with pomalidomide, bortezomib or SAHA induces synergistic anti-MM activity. Our results provide the rationale for translation of RRx-001, either alone or in combination, to clinical evaluation in MM.

Topics: Animals; Antineoplastic Agents; Apoptosis; Azetidines; Bortezomib; DNA (Cytosine-5-)-Methyltransferase 1; DNA (Cytosine-5-)-Methyltransferases; Drug Resistance, Neoplasm; Drug Synergism; Epigenomics; Heterografts; Humans; Hypoxia; Mice; Multiple Myeloma; Nitro Compounds; Thalidomide; Ubiquitin Thiolesterase; Ubiquitin-Specific Peptidase 7