Haptoglobin-related protein (HPR)

Haptoglobin-related protein (HPR) is a plasma protein encoded by the HPR gene in humans, closely related to haptoglobin (HP). It binds hemoglobin with high affinity, forming complexes distinct from those of haptoglobin, and acts as a component of trypanosome lytic factor-1 (TLF-1) along with apolipoprotein L1, mediating innate immune protection against African trypanosomes (agents of sleeping sickness). HPR does not facilitate clearance of hemoglobin via the CD163 receptor as haptoglobin does, meaning its hemoglobin complex persists longer in the plasma. Elevated levels of HPR or its gene copy number may be protective against trypanosome infection and could serve as a biomarker for breast cancer recurrence risk. No approved drugs directly target HPR, and no direct therapeutic safety concerns are documented. HPR is primarily considered an innate immune mediator, rather than a receptor, enzyme, or transporter.

Other names

Haptoglobin-related proteinHPRA-259H10.2HPhaptoglobin-related proteinHaptoglobin-related locus

No drug mechanisms targeting HPR directly, but HPR—through TLF-1—contributes to trypanosome lysis in innate immunity.