How to get CIE Lab values from an icc profile?

Question

If I have cmyk values and a cmyk icc profile. Can I obtain CIE Lab values for an icc profile.

I try to use little CMS, but I always get incorrect Lab values.

cmsHPROFILE profile = cmsOpenProfileFromFile("SWOP2013C5.icc", "r");
cmsHTRANSFORM xform = cmsCreateTransform(profile, TYPE_CMYK_FLT, 
                                         NULL, TYPE_Lab_FLT, INTENT_PERCEPTUAL, 0);

float cmykValues[] = {100.0, 0.0, 0.0, 0,0};
float labValues[3];
cmsDoTransform(xform, cmykValues, labValues, 1);

Thanks