GCG and type 1 diabetes mellitus: In SAXA group, rs10305439, rs10305441 of GLP1R and rs6233 of PCSK1/3 were associated with HbA1c response (p = 0.026, 0.019, and 0.048 respectively); the G allele of rs2143734 of GLP1R were associated with lower change of fasting C-peptide from baseline (p = 0.029) CONCLUSIONS: The saxagliptin did not ameliorate glucose fluctuations; however, it appeared to maintain β-cell function to some extent, and SNPs in the incretin-related gene may indicate responsiveness to DPP-IV inhibitors in T1DM.<h4>Clinicaltrials</h4>Gov number, NCT02307695.