With Improved GVHD Prophylaxis, Stem Cell Transplants Are Still Successful With Less HLA, Matching, Says Researcher

In this second excerpt from an interview with Managed Healthcare Executive (MHE), Antonio Jimenez Jimenez, M.D., of the Sylvester Comprehensive Cancer Center at the University of Miami Miller School of Medicine, discusses human leukocyte antigen (HLA) matching, graft-vs-host disease prophylaxis and the donor registries.

Post-transplant cyclophosphamide (PTCy) has opened up transplants from less-than-perfectly matched HLA donors and recipients, but some HLA matching is still needed, Jimenez Jimenez explains. Eight-of-eight matching, when all eight HLA alleles (two at each of four loci) between the donor and recipient are matched, is considered a full match. Six-of-eight matching opens up many more options for suitable matches between donors and recipients. "When you get down to six out of eight, we know through modeling that you can find a donor irrespective of race or ethnicity," Jimenez Jimenez says. Because of the effectiveness of post-transplant cyclophosphamide graft-vs-host disease (GVHD) prophylaxis, clinicians are moving away from framing a closer HLA match as necessarily being better for the recipient. "We're trying to move away a little bit from the notion that seven out of eight or six out of eight is better than five out of eight. The data we have so far shows that when we use the PTCy platform, the degree of mismatch doesn't seem to matter very much," Jimenez

Jimenez says.

The high rates of GVHD were, historically, the main factors in the mortality rate among patients who received mismatched stem transplants, he says. "Five out of eight, six out of eight, and definitely four out of eight were just prohibitive" because of the mortality risk, Jimenez Jimenez told MHE. "Even if you could identify that donor a few years back, it really didn't mean much, because that was not a donor you were going to offer to any patient, no matter how bad their options were."