Octreotide Lar in Patients with Autosomal Dominant Polycystic Kidney Disease: From Bench to A Novel Perspective of Therapy

Polycystins 1 or 2 congenital defects result in impaired Ca2+ inflow through the tubular cell membrane with reduced intracellular Ca2+ concentration and secondary adenylcyclase over-activation with increased intracellular cAMP. This activates chloride-driven fluid secretion and tubular cell proliferation and de-differentiation with cyst formation and growth. Thus, medications, such as the somatostatin analogue Octreotide LAR or the vasopressin antagonist Tolvaptan, that reduce intracellular cAMP, have been tested to inhibit cAMP-mediated chloride secretion and cell proliferation in experimental and human polycystic kidney disease. Seminal studies conducted in the early ‘80s by Franklin Epstein showed that in the shark rectal gland chloride secretion is markedly inhibited by somatostatin in a way suggesting inhibition of adenylcyclase. Evidence that specific receptors for somatostatin, in particular the sst2 subtype, are present in tubular cell membranes suggested that Octreotide LAR binding to its specific renal receptors could exert similar effects in ADPKD cells. In a pilot, cross-over safety study we found that 6-month Octreotide LAR therapy was safe and well tolerated in 12 patients with ADPKD and significantly decreased total kidney volume growth as compared to placebo. Then, the ALADIN and ALADIN II academic, prospective, randomized, placebo-controlled clinical trials found that 3-year Octreotide LAR treatment significantly slowed total kidney and cyst volume growth. In ALADIN treatment slowed chronic decline of directly measured GFR in 79 patients with estimated GFR ≥ 40 ml/min/1.73 m2. In ALADIN II treatment slowed progression to doubling of serum creatinine or ESKD in 100 patients with stage 3b-4 CKD. Treatment was equally safe and well tolerated in both studies. Sub-studies also showed that 3-year Octreotide LAR therapy reduced total liver volume in 27 ADPKD patients with associated polycystic livers and improved left ventricular twisting and untwisting function in 34 ADPKD patients assessed by speckled-tracked echocardiography. Future trials should confirm the long-term benefits of Octreotide LAR in larger populations of ADPKD patients. Moreover, recent studies found that somatostatin analogues and Tolvaptan have additional beneficial effects in experimental polycystic kidney disease. Thus, clinical trials should also explore whether Octreotide LAR and Tolvaptan in combined therapy may have an additional beneficial effect even in human disease.