Aim: The development of selective and potent antitumor agents remains a significant challenge. This study aimed to synthesize and evaluate biaryl hydroxy-1,2,3-triazoles and 9H-fluorene-1,2,3-triazole hybrids, inspired by previously identified bioactive 1,2,3-triazoles, for their cytotoxic potential against human cancer cell lines. Methods: A library of 13 biaryl hydroxy-1,2,3-triazoles and 11 fluorene-1,2,3-triazoles was synthesized using optimized Suzuki and telescopic one-pot reactions, with yields ranging from 16% to 97%. The cytotoxicity of these compounds was tested against HCT-116 (colorectal cancer), SNB-19 (astrocytoma), MDA-MB-231 (triple-negative breast cancer), and MOLM-13 (acute myeloid leukemia, FLT3-ITD mutant) cell lines. Results: Two fluorene-triazoles, 1-(2-bromophenyl)-4-(9H-fluoren-9-yl)-1H-1,2,3-triazole (LSO258) and 1-(4-bromophenyl)-4-(2-fluoro-9H-fluoren-9-yl)-1H-1,2,3-triazole (LSO272), both containing bromine substituents, exhibited selective cytotoxicity against MOLM-13, with half-maximal inhibitory concentration (IC50) values of 25.5 μM and 12.5 μM, respectively. Furthermore, LSO258 and LS0272 showed a selectivity index ≥ 2 towards the MOLM-13 cell line. Biaryl hydroxy-1,2,3-triazoles displayed broader activity, with [1,1’-biphenyl]-2-yl(1-(2,5-dibromophenyl)-1H-1,2,3-triazol-4-yl)methanol (LSO278), featuring two bromine groups, demonstrating potency across HCT-116, MDA-MB-231, and MOLM-13 (IC50: 23.4 μM, 34.3 μM, and 18.7 μM, respectively). However, structural rigidity did not consistently predict activity, as 1-(2,5-dibromophenyl)-4-(9H-fluoren-9-yl)-1H-1,2,3-triazole (LSO275), a rigid fluorene-triazole, was inactive. MOLM-13 was the most sensitive cell line, with compounds such as 4-(9H-fluoren-9-yl)-1-(4-(trifluoromethyl)phenyl)-1H-1,2,3-triazole (LSO259) and (1-(4-bromophenyl)-1H-1,2,3-triazol-4-yl)(4’-fluoro-[1,1’-biphenyl]-2-yl)methanol (LSO280), achieving maximum growth inhibition (MGI > 55%) despite not reaching IC50 values. Conclusions: The results highlight the critical role of bromine substitution on the aryl azide-derived ring in modulating cytotoxic activity. The study reinforces the potential of rigid fluorene-based scaffolds as promising leads for the development of targeted therapies against FLT3-mutant leukemia, aligning with previous reports on 1,2,3-triazole hybrids antiproliferative activity in leukemia models.

Background: The potentiator VX-770 (ivacaftor) has been approved as a monotherapy for over 95 cystic fibrosis (CF)-causing variants associated with gating/conductance defects of the CF transmembrane conductance regulator (CFTR) channel. However, despite its therapeutic success, VX-770 only partially restores CFTR activity for many of these variants, indicating they may benefit from the combination of potentiators exhibiting distinct mechanisms of action (i.e., co-potentiators). We previously identified LSO-24, a hydroxy-1,2,3-triazole-based compound, as a modest potentiator of p.Arg334Trp-CFTR, a variant with a conductance defect for which no modulator therapy is currently approved. Objective/Methods: We synthesized a new set of LSO-24 structure-based compounds, screened their effects on p.Arg334Trp-CFTR activity, and assessed the additivity of hit compounds to VX-770, ABBV-974, ABBV-3067, and apigenin. After validation by electrophysiological assays, the most promising hits were also assessed in cells expressing other variants with defective gating/conductance, namely p.Pro205Ser, p.Ser549Arg, p.Gly551Asp, p.Ser945Leu, and p.Gly1349Asp. Results: We found that five compounds were able to increase p.Arg334Trp-CFTR activity with similar efficacy, but slightly greater potency promoted by LSO-150 and LSO-153 (EC₅₀: 1.01 and 1.26 μM, respectively). These two compounds also displayed a higher rescue of p.Arg334Trp-CFTR activity in combination with VX-770, ABBV-974, and ABBV-3067, but not with apigenin. When tested in cells expressing other CFTR variants, LSO-24 and its derivative LSO-150 increased CFTR activity for the variants p.Ser549Arg, p.Gly551Asp, and p.Ser945Leu with a further effect in combination with VX-770 or ABBV-3067. No potentiator was able to rescue CFTR activity in p.Pro205Ser-expressing cells, while p.Gly1349Asp-CFTR responded to VX-770 and ABBV-3067 but not to LSO-24 or LSO-150. Conclusions: Our data suggest that these new potentiators might share a common mechanism with apigenin, which is conceivably distinct from that of VX-770 and ABBV-3067. The additive rescue of p.Arg334Trp-, p.Ser549Arg-, p.Gly551Asp-, and p.Ser945Leu-CFTR also indicates that these variants could benefit from the development of a co-potentiator therapy.