Animal studies of Endocyte's ($ECYT) delivery system for rapamycin, an immunosuppressant, have shown the first hints of efficacy in kidney disease. While this is very early stage research, it could offer hope to the 12 million people worldwide who are affected by autosomal-dominant polycystic kidney disease (ADPKD, or PKD), an inherited disorder that leads to growth of cysts throughout the kidney, which eventually cause it to stop working. There is currently no treatment for ADPKD, and patients eventually need dialysis or a transplant.
The drawback of using rapamycin in APKD is that it is difficult to get the concentration high enough in the kidney while keeping the side effects low. Endocyte has created FC-rapa, (EC0371) by linking rapamycin to folate in what it describes as a small molecule drug conjugate (SMDC). The cells lining the cysts in the kidney have receptors for folate, and so the drug is taken up into the kidney.
In a study published in the Journal of the American Society of Nephrology, the researchers gave EC0371 to mice with kidney disease and found that it cut the growth of cysts and reduced the damage to kidney function. Rapamycin works by inhibiting mTOR activity, but the researchers did not see any affect on mTOR in organs other than the kidney, suggesting that EC0371 might have fewer side effects than rapamycin.
"Being a PKD patient myself, I have experienced the unmet medical need first hand," said Christopher Leamon, vice president of R&D at Endocyte. "Our results with EC0371 are very exciting, demonstrating that we may be able to reduce the side effects observed in the clinical trials with untargeted rapamycin by delivering the drug directly to the cystic cells. What we have observed here also reinforces Endocyte's concept of targeted drug delivery."
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