  We calculate the two-loop flavor-singlet axial-vector and gluon transversity
coefficient functions for deeply virtual Compton scattering in QCD. We observe
interesting properties regarding the transcendentality of the transversity
coefficient function. Our results complete the calculation of the full
next-to-next-to-leading order coefficient function in deeply virtual Compton
scattering. Numerically, the two-loop corrections in the axial-vector and
transversity channel are comparable to their vector counterpart at moderate
skewness parameter {\xi} and hence indispensable for analyzing the upcoming
high-precision data from the Electron-Ion Collider.
