Quizartinib (AC220) is an orally bioavailable, small molecule receptor tyrosine kinase inhibitor that is being developed by Daiichi Sankyo Company (previously Ambit Biosciences) and Astellas Pharma as a treatment for acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL) and advanced solid tumours. The highest affinity target identified for Quizartinib was FLT3. The only other kinases with binding constants within 10-fold that for FLT3 were the closely related receptor tyrosine kinases KIT, PDGFRA, PDGFRB, RET, and CSF1R. Kinase inhibition of (mutant) KIT, PDGFR and FLT3 isoforms by quizartinib leads to potent inhibition of cellular proliferation and induction of apoptosis in in vitro leukemia models as well as in native leukemia blasts treated ex vivo.

PF-04449913 is a potent and selective inhibitor of the Hh signaling pathway through binding to the target, smoothened. PF-04449913 inhibits Hh signaling in vitro and has demonstrated significant antitumor activity in vivo. In the clinic, PF-04449913 is being evaluated both in hematological and solid malignancies, with a phase II trial currently underway in both fit and unfit patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS). Treatment-related adverse-events were nausea, dizziness, somnolence, QT prolongation and pruritus. Based on pre-clinical assessments, CYP3A4 is believed to be primarily involved in the metabolism of PF-04449913 that is why PF-04449913 plasma exposures and peak concentrations were increased following concurrent administration of ketoconazole (CYP3A4 inhibitor).

Midostaurin, a derivate of staurosporine (N-benzoylstaurosporine), is a broad-spectrum inhibitor of Ser/Thr and Tyr protein kinases. Midostaurin showed broad antiproliferative activity against various tumor and normal cell lines in vitro and is able to reverse the p-glycoprotein-mediated multidrug resistance of tumor cells in vitro. Midostaurin showed in vivo antitumor activity as single agent and inhibited angiogenesis in vivo. At the end of 2016 FDA granted Priority Review to the PKC412 (midostaurin) new drug application (NDA) for the treatment of acute myeloid leukemia (AML) in newly-diagnosed adults with an FMS-like tyrosine kinase-3 (FLT3) mutation, as well as for the treatment of advanced systemic mastocytosis (SM).

Decitabine was first synthesized by Pliml and Sorm in the Institute of Organic Chemistry, Czechoslovak Academy of Sciences in 1964. Later, the drug was approved by FDA for the treatment of myelodysplastic syndromes in patients with cancer. Upon administration the decitabine is metabolized to the active phosphorylated metabolite which is incorporated into DNA and thus inhibits DNA methyltransferase (decitabine deplete DNMT1).

Lenalidomide (trade name Revlimid) is a derivative of thalidomide introduced in 2004. It is an immunomodulatory agent with anti-angiogenic properties. Revlimid in combination with dexamethasone is indicated for the treatment of patients with multiple myeloma (MM) who have received at least one prior therapy. Also is indicated for the treatment of patients with transfusion-dependent anemia due to low- or intermediate-1-risk myelodysplastic syndromes (MDS) associated with a deletion 5q cytogenetic abnormality with or without additional cytogenetic abnormalities. In addition, Revlimid is indicated for the treatment of patients with mantle cell lymphoma (MCL) whose disease has relapsed or progressed after two prior therapies, one of which included bortezomib. The mechanism of action of lenalidomide remains to be fully characterized. Lenalidomide inhibited the secretion of pro-inflammatory cytokines and increased the secretion of anti-inflammatory cytokines from peripheral blood mononuclear cells. Lenalidomide causes a delay in tumor growth in some in vivo nonclinical hematopoietic tumor models including multiple myeloma. Immunomodulatory properties of lenalidomide include activation of T cells and natural killer (NK) cells, increased numbers of NKT cells, and inhibition of pro-inflammatory cytokines (e.g., TNF-α and IL-6) by monocytes. In multiple myeloma cells, the combination of lenalidomide and dexamethasone synergizes the inhibition of cell proliferation and the induction of apoptosis. Recently was discovered, that protein cereblon (CRBN) is a proximate, therapeutically important molecular target of lenalidomide. Low CRBN expression was found to correlate with drug resistance in multiple myeloma (MM) cell lines and primary MM cells. One of the downstream targets of CRBN identified is interferon regulatory factor 4 (IRF4), which is critical for myeloma cell survival and is down-regulated by (immune-modulatory drugs) treatment. CRBN is also implicated in several effects of immunomodulatory drugs, such as down-regulation of tumor necrosis factor-α (TNF-α) and T cell immunomodulatory activity, demonstrating that the pleotropic actions of the immunomodulatory drugs (IMiDs) are initiated by binding to CRBN. Future dissection of CRBN downstream signaling will help to delineate the underlying mechanisms for IMiD action and eventually lead to development of new drugs with more specific anti-myeloma activities. It may also provide a biomarker to predict IMiD response and resistance. Lenalidomide also inhibited the expression of cyclooxygenase-2 (COX-2) but not COX-1 in vitro.

Azacitidine (Vidaza; Pharmion), an inhibitor of DNA methylation, was approved by the US FDA for the treatment of myelodysplastic syndromes in May 2004. It is the first drug to be approved by the FDA for treating this rare family of bone-marrow disorders, and has been given orphan-drug status. It is also a pioneering example of an agent that targets 'epigenetic' gene silencing, a mechanism that is exploited by cancer cells to inhibit the expression of genes that counteract the malignant phenotype. VIDAZA is used for the treatment of patients with the following FAB myelodysplastic syndrome (MDS) subtypes: Refractory anemia (RA) or refractory anemia with ringed sideroblasts (RARS), refractory anemia with excess blasts (RAEB), refractory anemia with excess blasts in transformation (RAEB-T), and chronic myelomonocytic leukemia (CMMoL). Azacitidine is a pyrimidine nucleoside analog of cytidine. It is believed to exert its antineoplastic effects by causing hypomethylation of DNA and direct cytotoxicity on abnormal hematopoietic cells in the bone marrow. The concentration of azacitidine required for maximum inhibition of DNA methylation in vitro does not cause major suppression of DNA synthesis. Hypomethylation may restore normal function to genes that are critical for differentiation and proliferation. As azacitidine is a ribonucleoside, it incorporates into RNA to a larger extent than into DNA. The incorporation into RNA leads to the dissemble of polyribosomes, defective methylation and acceptor function of transfer RNA, and inhibition of the production of protein. Its incorporation into DNA leads to a covalent binding with DNA methyltransferases, which prevents DNA synthesis and subsequent cytotoxicity. The cytotoxic effects of azacitidine cause the death of rapidly dividing cells, including cancer cells that are no longer responsive to normal growth control mechanisms. Non-proliferating cells are relatively insensitive to azacitidine.

Ezatiostat (TLK199) [γ-glutamyl-S-(benzyl)cysteinyl-R-phenyl glycine diethyl ester] is an inhibitor of Glutathione S-transferase P1–1 (GSTπ). The drug is a peptidomimetic of GSH (glutathione), esterified to enhance cellular uptake and designed to bind to the “G-site” of GSTP1–1. Independent of catalysis inhibition, TLK199 also disrupts the protein:protein interaction site(s) between GSTP1–1 and JNK1. Telik Inc was developing TLK-199 for the potential prevention of myelosuppression in blood diseases, namely myelodysplastic syndrome.

Talmapimod is a p38 MAPK kinase inhibitor that inhibits p38 alpha with IC50 value of 9 nM which is 10-times lower then IC50 for p38 beta. Talmapimod was under clinical development for the treatment of Myelodysplastic Syndromes, Multiple Myeloma and Rheumatoid Arthritis (phase II), however, it seems to be discontinued as no longer presents in Janssen's pipeline.

Mocetinostat is an rationally designed, orally available, Class 1-selective, small molecule, 2-aminobenzamide HDAC inhibitor with potential antineoplastic activity. Mocetinostat binds to and inhibits Class 1 isoforms of HDAC, specifically HDAC 1, 2 and 3, which may result in epigenetic changes in tumor cells and so tumor cell death; although the exact mechanism has yet to be defined, tumor cell death may occur through the induction of apoptosis, differentiation, cell cycle arrest, inhibition of DNA repair, upregulation of tumor suppressors, down regulation of growth factors, oxidative stress, and autophagy, among others. It is undergoing clinical trials for treatment of various cancers including bladder cancer, diffuse large B cell lymphoma, follicular lymphoma, myelodysplastic syndromes, non-small cell lung cancer. Fatigue, weight loss or anorexia were most common treatment-related adverse events.

CPI-0610 is a small molecule inhibitor of the Bromodomain and Extra-Terminal (BET) family of proteins, with potential antineoplastic activity. Upon administration, the BET inhibitor CPI-0610 binds to the acetylated lysine recognition motifs on the bromodomain of BET proteins, thereby preventing the interaction between the BET proteins and acetylated histone peptides. This disrupts chromatin remodeling and gene expression. Prevention of the expression of certain growth-promoting genes may lead to an inhibition of tumor cell growth. CPI-0610 is currently being evaluated in three Phase 1 clinical trials in the U.S.