CHMFL-26 is a highly potent irreversible HER2 inhibitor for use in the treatment of HER2-positive and HER2-mutant cancers.

Oncogene HER2 is amplified in 20%-25% of human breast cancers and 6.1%-23.0% of gastric cancers, and HER2-directed therapy significantly improves the outcome for patients with HER2-positive cancers. However, drug resistance is still a clinical challenge due to primary or acquired mutations and drug-induced negative regulatory feedback. In this study, we discovered a potent irreversible HER2 kinase inhibitor, CHMFL-26, which covalently targeted cysteine 805 of HER2 and effectively overcame the drug resistance caused by HER2 V777L, HER2 L755S, HER2 exon 20 insertions, and p95-HER2 truncation mutations. CHMFL-26 displayed potent antiproliferation efficacy against HER2-amplified and mutant cells through constant HER2-mediated signaling pathway inhibition and apoptosis induction. In addition, CHMFL-26 suppressed tumor growth in a dose-dependent manner in xenograft mouse models. Together, these results suggest that CHMFL-26 may be a potential novel anti-HER2 agent for overcoming drug resistance in HER2-positive cancer therapy.

Antimicrobial activity of a honeybee (Apis cerana) venom Kazal-type serine protease inhibitor.

Insect-derived Kazal-type serine protease inhibitors exhibit thrombin, elastase, plasmin, proteinase K, or subtilisin A inhibition activity, but so far, no functional roles for bee-derived Kazal-type serine protease inhibitors have been identified. In this study, a bee (Apis cerana) venom Kazal-type serine protease inhibitor (AcKTSPI) that acts as a microbial serine protease inhibitor was identified. AcKTSPI contained a single Kazal domain that displayed six conserved cysteine residues and a P1 threonine residue. AcKTSPI was expressed in the venom gland and was present as a 10-kDa peptide in bee venom. Recombinant AcKTSPI Kazal domain (AcKTSPI-Kd) expressed in baculovirus-infected insect cells demonstrated inhibitory activity against subtilisin A (Ki 67.03 nM) and proteinase K (Ki 91.53 nM), but not against α-chymotrypsin or trypsin, which implies a role for AcKTSPI as a microbial serine protease inhibitor. However, AcKTSPI-Kd exhibited no detectable inhibitory effects on factor Xa, thrombin, tissue plasminogen activator, or elastase. Additionally, AcKTSPI-Kd bound directly to Bacillus subtilis, Bacillus thuringiensis, Beauveria bassiana, and Fusarium graminearum but not to Escherichia coli. Consistent with these findings, AcKTSPI-Kd showed antibacterial activity against Gram-positive bacteria and antifungal activity against both plant-pathogenic and entomopathogenic fungi. These findings constitute molecular evidence that AcKTSPI acts as an inhibitor of microbial serine proteases. This paper provides a novel view of the antimicrobial functions of a bee venom Kazal-type serine protease inhibitor.

A spider-derived Kunitz-type serine protease inhibitor that acts as a plasmin inhibitor and an elastase inhibitor.

Kunitz-type serine protease inhibitors are involved in various physiological processes, such as ion channel blocking, blood coagulation, fibrinolysis, and inflammation. While spider-derived Kunitz-type proteins show activity in trypsin or chymotrypsin inhibition and K(+) channel blocking, no additional role for these proteins has been elucidated. In this study, we identified the first spider (Araneus ventricosus) Kunitz-type serine protease inhibitor (AvKTI) that acts as a plasmin inhibitor and an elastase inhibitor. AvKTI possesses a Kunitz domain consisting of a 57-amino-acid mature peptide that displays features consistent with Kunitz-type inhibitors, including six conserved cysteine residues and a P1 lysine residue. Recombinant AvKTI, expressed in baculovirus-infected insect cells, showed a dual inhibitory activity against trypsin (K(i) 7.34 nM) and chymotrypsin (K(i) 37.75 nM), defining a role for AvKTI as a spider-derived Kunitz-type serine protease inhibitor. Additionally, AvKTI showed no detectable inhibitory effects on factor Xa, thrombin, or tissue plasminogen activator; however, AvKTI inhibited plasmin (K(i) 4.89 nM) and neutrophil elastase (K(i) 169.07 nM), indicating that it acts as an antifibrinolytic factor and an antielastolytic factor. These findings constitute molecular evidence that AvKTI acts as a plasmin inhibitor and an elastase inhibitor and also provide a novel view of the functions of a spider-derived Kunitz-type serine protease inhibitor.

Anti-elastolytic activity of a honeybee (Apis cerana) chymotrypsin inhibitor.

The honeybee is an important insect species in global ecology, agriculture, and alternative medicine. While chymotrypsin and trypsin inhibitors from bees show activity against cathepsin G and plasmin, respectively, no anti-elastolytic role for these inhibitors has been elucidated. In this study, we identified an Asiatic honeybee (Apis cerana) chymotrypsin inhibitor (AcCI), which was shown to also act as an elastase inhibitor. AcCI was found to consist of a 65-amino acid mature peptide that displays ten cysteine residues. When expressed in baculovirus-infected insect cells, recombinant AcCI demonstrated inhibitory activity against chymotrypsin (K(i) 11.27 nM), but not trypsin, defining a role for AcCI as a honeybee-derived chymotrypsin inhibitor. Additionally, AcCI showed no detectable inhibitory effects on factor Xa, thrombin, plasmin, or tissue plasminogen activator; however, AcCI inhibited human neutrophil elastase (K(i) 61.05 nM), indicating that it acts as an anti-elastolytic factor. These findings constitute molecular evidence that AcCI acts as a chymotrypsin/elastase inhibitor.