Although human
islet transplantation has proven to provide clinical benefits, especially the near complete amelioration of
hypoglycemia, the supply of human islets is limited and insufficient to meet the needs of all people that could benefit from
islet transplantation. Porcine islets, secreting
insulin nearly identical to that of human
insulin, have been proposed as a viable supply of unlimited islets. Further, encapsulation of the porcine islets has been shown to reduce or eliminate the use of immunosuppressive therapy that would be required to prevent rejection of the foreign islet tissue. The goal of the current study was to determine the long-term safety and efficacy of
agarose encapsulated porcine islets (macrobeads) in diabetic cynomolgus macaques, in a study emulating a proposed IND trial in which daily exogenous
insulin therapy would be reduced by 50% with no loss of
glucose regulation. Four of six animals implanted with macrobeads demonstrated ≥ 30% reduction in
insulin requirements in year 1 of follow-up. Animals were followed for 2, 3.5, and 7.4 years with no serious adverse events, mortality or evidence of pathogen transmission. This study supports the continued pursuit of encapsulated porcine islet
therapy as a promising treatment option for
diabetes mellitus.