Degrading FLT3-ITD protein by proteolysis targeting chimera (PROTAC).

Clinical FLT3 mutations caused poor therapeutic benefits toward the present FLT3 inhibitors, and degradation of the FLT3 mutant protein may be a promising alternative approach to protect against acute myeloid leukemia (AML). Herein, we report the discovery of small molecule FLT3 degraders based on the proteolysis targeting chimera (PROTAC). FLT3 degraders were designed, synthesized, and evaluated for FLT3 degradation. Promising PF15 significantly inhibited the proliferation of FLT3-ITD-positive cells, induced FLT3 degradation and downregulated the phosphorylation of FLT3 and STAT5. An in vivo xenograft model and survival period evaluation verified the efficacy of PROTAC. These findings laid a robust foundation for FLT3-PROTAC molecules as an effective strategy for treating AML.

Design, synthesis and biological evaluation of thioether-containing lenalidomide and pomalidomide derivatives with anti-multiple myeloma activity.

Lenalidomide and its analogs are well-known for treating multiple myeloma. In this work, designed sulfide-modified lenalidomide and pomalidomide were synthesized and evaluated. The anti-proliferative activity against MM.1S cell line of 3ak (IC50 = 79 nM) was similar to lenalidomide (IC50 = 81 nM). Compared to benzylic thioether substituted lenalidomide 3a, the half-live (T1/2) of 4-F-phenyl-thioether analogs 3ak in human liver microsomes was promoted from 3 min to 416.7 min. The corresponding metabolic factor of 3ak was increased from 2.8% to 79.5%, which was slightly lower than lenalidomide (91.5%). Moreover, the IKZF1 degradation of 3y and 3ak was well related with corresponding IC50 values, which suggested the IKZF1 degradation efficiency is correlated to the responses of MM1. S cells. Furthermore, the oral administration of compounds 3y and 3ak at dosages of 60 mg/kg could delay tumor growth in female CB-17 SCID mice. This research helped to prompt the stability of thioether lenalidomide analogs, which paved the way for developing better molecules for treating multiple myeloma.

Design and synthesis of new lenalidomide analogs via Suzuki cross-coupling reaction.

Lenalidomide is a cereblon modulator known for its antitumor, anti-inflammatory, and immunomodulatory properties in clinical applications. Recently, some reported lenalidomide analogs could exhibit a significant bioactivity through various modifications in the isoindolinone ring. In this study, we designed and synthesized a series of novel lenalidomide analogs on the basis of the installation of a methylene chain at the C-4 position of isoindolinone via the Suzuki cross-coupling reaction. These new compounds were further evaluated for their in vitro antiproliferative activities against two tumor cell lines (MM.1S and Mino). Specifically, compound 4c displayed the strongest antiproliferative activity against the MM.1S (IC50 = 0.27 ± 0.03 µM) and Mino (IC50 = 5.65 ± 0.58 µM) tumor cell lines. In summary, we have developed a new synthetic strategy for C-4 derivatization of lenalidomide, providing a bioactive scaffold that could be used to discover further potential antitumor lead compounds in pharmaceutical research.

Discovery of a new class of PROTAC BRD4 degraders based on a dihydroquinazolinone derivative and lenalidomide/pomalidomide.

BRD4 has emerged as an attractive target for anticancer therapy. However, BRD4 inhibitors treatment leads to BRD4 protein accumulation, together with the reversible nature of inhibitors binding to BRD4, which may limit the efficacy of BRD4 inhibitors. To address these problems, a protein degradation strategy based on the proteolysis targeting chimera (PROTAC) technology has been developed to target BRD4 recently. Herein, we present our design, synthesis and biological evaluation of a new class of PROTAC BRD4 degraders, which were based on a potent dihydroquinazolinone-based BRD4 inhibitor compound 6 and lenalidomide/pomalidomide as ligand for E3 ligase cereblon. Gratifyingly, several compounds showed excellent inhibitory activity against BRD4, and high anti-proliferative potency against human monocyte lymphoma cell line THP-1. Especially, compound 21 (BRD4 BD1, IC50 = 41.8 nM) achieved a submicromolar IC50 value of 0.81 µM in inhibiting the growth of THP-1 cell line, and was 4 times more potent than compound 6. Moreover, the mechanism study established that 21 could effectively induce the degradation of BRD4 protein and suppression of c-Myc. All of these results suggested that 21 was an efficacious BRD4 degrader for further investigation.

Design, synthesis and biological evaluation of the thioether-containing lenalidomide analogs with anti-proliferative activities.

Lenalidomide and its analogs have exhibited extensive anti-tumor, anti-inflammatory and immunomodulatory properties in pharmaceutical research. In this work, a series of novel thioether-containing lenalidomide analogs were designed and synthesized for biological evaluation. Lenalidomide showed significant anti-proliferative activity against the MM.1S cell line (IC50 = 50 nM) while it displayed no anti-proliferative activity against other treated tumor cell lines. Compared with lenalidomide, compound 3j exhibited preferable anti-proliferative activity against the MM.1S (IC50 = 1.1 nM), Mino (IC50 = 2.3 nM) and RPMI 8226 cell lines (IC50 = 5.5 nM). In addition, compound 3j displayed selective anti-proliferative activity against several tumor cell lines, including various B-NHL, MM and AML cell lines, and showed no cytotoxicity on the normal human cell line PBMC, suggesting a good safety profile. Following oral administration, compound 3j achieved a Cmax of 283 ng/mL at 0.83 h, and had a higher relative oral bioavailability value (F = 39.2%) than that of CC-220 (F = 22.8%), but its oral exposure in vivo was somewhat low (AUC = 755 h ng/mL). Furthermore, it was found that oral administration of compound 3j at dosages of 60 mg/kg could delay RPMI 8226 tumor growth in the female CB-17 SCID mice. The current work confirmed that installing thioether moiety at the 4-position of isoindolinone is an effective strategy for identifying new promising lenalidomide analogs with anti-tumor activities in preclinical study.