Development of HDAC Inhibitors Exhibiting Therapeutic Potential in T-Cell Prolymphocytic Leukemia

Epigenetic targeting has emerged as an efficacious therapy for hematological cancers. The rare and incurable T-cell prolymphocytic leukemia (T-PLL) is known for its aggressive clinical course. Current epigenetic agents such as histone deacetylase (HDAC) inhibitors are increasingly used for targeted therapy. Through a structure-activity relationship (SAR) study, we developed an HDAC6 inhibitor KT-531, which exhibited higher potency in T-PLL compared to other hematological cancers. KT-531 displayed strong HDAC6 inhibitory potency and selectivity, on-target biological activity, and a safe therapeutic window in nontransformed cell lines. In primary T-PLL patient cells, where HDAC6 was found to be overexpressed, KT-531 exhibited strong biological responses, and safety in healthy donor samples. Notably, combination studies in T-PLL patient samples demonstrated KT-531 synergizes with approved cancer drugs, bendamustine, idasanutlin, and venetoclax. Our work suggests HDAC inhibition in T-PLL could afford sufficient therapeutic windows to achieve durable remission either as standalone or in combination with targeted drugs.Peer reviewe

Advances in covalent kinase inhibitors.

Over the past decade, covalent kinase inhibitors (CKI) have seen a resurgence in drug discovery. Covalency affords a unique set of advantages as well as challenges relative to their non-covalent counterpart. After reversible protein target recognition and binding, covalent inhibitors irreversibly modify a proximal nucleophilic residue on the protein via reaction with an electrophile. To date, the acrylamide group remains the predominantly employed electrophile in CKI development, with its incorporation in the majority of clinical candidates and FDA approved covalent therapies. Nonetheless, in recent years considerable efforts have ensued to characterize alternative electrophiles that exhibit irreversible or reversibly covalent binding mechanisms towards cysteine thiols and other amino acids. This review article provides a comprehensive overview of CKIs reported in the literature over a decade period, 2007-2018. Emphasis is placed on the rationale behind warhead choice, optimization approach, and inhibitor design. Current FDA approved CKIs are also highlighted, in addition to a detailed analysis of the common trends and themes observed within the listed data set

Blocking STAT3/5 through direct or upstream kinase targeting in leukemic cutaneous T-cell lymphoma

Leukemic cutaneous T-cell lymphomas (L-CTCL) are lymphoproliferative disorders of skin-homing mature T-cells causing severe symptoms and high mortality through chronic inflammation, tissue destruction, and serious infections. Despite numerous genomic sequencing efforts, recurrent driver mutations have not been identified, but chromosomal losses and gains are frequent and dominant. We integrated genomic landscape analyses with innovative pharmacologic interference studies to identify key vulnerable nodes in L-CTCL. We detected copy number gains of loci containing the STAT3/5 oncogenes in 74% (n = 17/23) of L-CTCL, which correlated with the increased clonal T-cell count in the blood. Dual inhibition of STAT3/5 using small-molecule degraders and multi-kinase blockers abolished L-CTCL cell growth in vitro and ex vivo, whereby PAK kinase inhibition was specifically selective for L-CTCL patient cells carrying STAT3/5 gains. Importantly, the PAK inhibitor FRAx597 demonstrated encouraging anti-leukemic activity in vivo by inhibiting tumor growth and disease dissemination in intradermally xenografted mice. We conclude that STAT3/5 and PAK kinase interaction represents a new therapeutic node to be further explored in L-CTCL