The present invention includes pyrazolopyrimidine compounds of Formula I that selectively inhibit Mer tyrosine kinase (MerTK) activity and/or Tyro3 tyrosine kinase activity, and use of these pyrazolopyrimidine compounds as anti-cancer agents, immunostimulatory and immunomodulatory agents, anti-platelet agents, anti-infective agents, and as adjunctive agents in combination with chemotherapeutic, radiation or other standard of care for neoplasms.