Kinetic Steering of Amyloid Formation and Polymorphism by Canagliflozin, a Type-2 Diabetes Drug 2025
Amyloid formation is involved in widespread health conditions such as Alzheimer’s disease, Parkinson’s disease, and type-2 diabetes. Amyloid fibrils have a similar cross-β architecture, but fibrils formed by a single protein sequence can have diverse structures, varying with time, self-assembly conditions, and sequence modifications. Fibril structure has been proposed to be diagnostic of disease, but why different structures result under different conditions, especially in vitro, remains elusive. We previously identified a small molecule, YX-I-1, which inhibits in vitro amyloid formation by islet amyloid polypeptide (IAPP), a peptide hormone whose amyloid formation is involved in type-2 diabetes. Here, using YX-I-1 as a lead, we identified regulator-approved drugs with similar structures by chemical similarity analysis and substructure searches, and monitored the effect of 24 of these potential ligands on IAPP amyloid assembly in vitro. We show that one such compound, canagliflozin (Invokana), a type-2 diabetes drug already in clinical use, can strongly delay the kinetics of IAPP amyloid formation, an activity independent of its intended mode of action (sodium-glucose linked transporter 2 (SGLT2) inhibitor) that may have important therapeutic implications. Combining analysis of amyloid self-assembly kinetics, biophysical characterization of monomer and fibril binding, and cryo-EM of the assembly products, we show that YX-I-1 and canagliflozin target IAPP early in aggregation, remodeling the energy landscape of primary nucleation and profoundly altering the resulting fibril structures. Early binding events thus imprint long-lasting effects on the amyloid structures that form.
However, two of the small molecules – doxazosin, an alpha-1 blocker used to treat hypertension and benign prostatic hyperplasia, and canagliflozin, one of the three most widely used flozins for treatment of type-2 diabetes via its action as an SGLT2 inhibitor – caused a pronounced and statistically significant inhibition (fold-change in half-time of 1.61 ± 0.29, p < 0.0001 and 1.55 ± 0.22, p < 0.0001, respectively), comparable to the inhibition observed for YX-I-1 (fold-change in halftime of 1.49 ± 0.18, p < 0.0001) (Table S7, Fig. S6). Canagliflozin and doxazosin are structurally distinct, but both possess a high degree of structural similarity to YX-I-1 enantiomer 1 as assessed by ROCS, with ComboScores of 0.759 (Table S1) and 0.864 (Table S2), respectively. The presence of shared tetrahydropyran and phenyl substructures makes this similarity particularly obvious for canagliflozin (Fig. 1c, Fig. 2c), but comparison of the ComboScores indicates that doxazosin nonetheless has a higher overall degree of shape and pharmacophoric similarity to YX-I-1, despite the aligned substructures being different (Fig. 2c).
Dapagliflozin (Fig. 5d), one of the closest analogs of canagliflozin in the screening set, showed a pattern of binding similar to canagliflozin, with greater attenuation of the aromatic protons compared to the aliphatic protons, but binding was weaker overall and inversion of the aromatic peaks did not occur.
Here, we have investigated whether regulator-approved small molecule drugs can be repurposed as inhibitors of IAPP amyloid formation, building upon our previous work that identified YX-I-1 as a lead26. Virtual screening, ThT assays and biophysical characterization successfully identified two widely used FDA-approved drugs, canagliflozin and doxazosin, as inhibitors of IAPP amyloid formation. Canagliflozin, currently used as a third-line type-2 diabetes medication with an intended mode of action (SGLT2 inhibitor) unrelated to islet amyloid, had the strongest inhibitory effect of all molecules tested. Whether treatment with canagliflozin provides additional clinically relevant benefits through an effect on IAPP fibrillization is unknown, although canagliflozin has been shown to improve pancreatic β-cell function via an uncharacterized SGLT2-independent mechanism. On the other hand, canagliflozin may currently be given too late in disease progression to take advantage of any therapeutic benefits by inhibiting IAPP amyloid formation. In addition, ex vivo structure determination of IAPP fibril deposits and clinical/animal studies will be required to determine whether canagliflozin treatment results in a change in IAPP fibril polymorphism in patients, and whether this affects disease outcomes. Doxazosin, on the other hand, is not currently used as a type-2 diabetes medication, but is widely used for conditions such as benign prostatic hyperplasia, and may also affect IAPP aggregation if administered to diabetic people with these conditions. As canagliflozin and doxazosin are both widely used drugs, and could be rapidly repurposed as amyloid-targeting type-2 diabetes treatments, the clinical effects of any current interactions with islet amyloid and the effects of early treatment in preor early-stage diabetic individuals should be investigated as a matter of urgency.
@DrFraser: I don’t understand the whole paper, but it’s one more datapoint in favor of SGLT2i (and specifically canagliflozin?) and alpha-blockers (and specifically doxazosin?). TBC…
