Extended Data Fig. 7|. Functional evaluation of the SPR blocker QM385.

a, The BH4 pathway, indicating how QM385 acts on SPR, limiting BH4 production and correspondingly increasing sepiapterin levels, which can be used as a biomarker for QM385-mediated SPR inhibition. b, c, A representative concentration-response curve showing the binding affinity of QM385 to human SPR, tested in vitro by TR-FRET (b); and reduction of BH4 levels upon QM385 treatment in anti-CD3/28-stimulated mouse splenocytes (left panel, two independent experiments) and human PBMCs (right panel, two independent experiments) (c). Indicated in red are the calculated IC₅₀ values for each assay. The binding-effect assay was repeated 162 independent times with similar results. d, The oxygen-uptake rate in permeabilized, 16-h anti-CD3/CD28-stimulated wild-type CD4⁺ T cells treated with DMSO or QM385 (2.5 μM). Data from individual mice (n = 3) are indicated ± s.e.m. ***P < 0.001 (two-tailed Student’s t-test). e, ATP measurements of unstimulated (n = 8) and 24-h-activated wild-type CD4⁺ T cells treated with DMSO vehicle (n = 4) or varying doses of QM385 (n = 4 for each dose). Data are shown as means ± s.e.m. NS, not significant; **P < 0.01 (one-way ANOVA with Dunnett’s multiple comparisons). f, Fold changes in DHE levels between CD4⁺ T cells treated with DMSO or QM385 (2.5 μM) and activated for 20 h. Data from individual mice (n = 4) are indicated ± s.e.m. **P < 0.01 (two-tailed Student’s t-test). g, Allergic airway inflammatory disease model and quantification of inflammatory cells in bronchoalveolar lavage fluids (BALFs). Data are shown as box-and-whisker plots (running from minimal to maximal values); individual data points are shown. n = 15 for vehicle-treated mice; n = 17 for QM385-treated mice. QM385 (1 mg kg^–1) was administered orally (peritoneally) twice a day for three consecutive days as depicted in the diagram. *P < 0.05; **P < 0.01 (two-tailed Student’s t-test). h, Proliferation of human CD4⁺ T cells from two donors performed in triplicate samples. Anti-CD3/28 T cells were stimulated with varying doses of QM385 and total counts were measured. Data are shown as means ± s.e.m. **P < 0.01; P < 0.05 (one-way ANOVA with Dunnett’s multiple comparisons).