However, good correlation is noted between trough concentration levels and drug exposure, known as area under the concentration-time curve, for both sirolimus (SRL) and tacrolimus (TAC) (SRL: r2 = 0.83; TAC: r2 = 0.82), so only one level need be taken to know its pharmacokinetic (PK) profile. PK profiles of SRL and of TAC are unaltered by simultaneous administration. Dose-corrected drug exposure of TAC correlates with SRL (r2 = 0.8), so patients have similar bioavailability of both. Chemistry
Sirolimus is a natural product and macrocyclic lactone. Biosynthesis
The biosynthesis of the rapamycin core is accomplished by a type I polyketide synthase (PKS) in conjunction with a nonribosomal peptide synthetase (NRPS). The domains responsible for the biosynthesis of the linear polyketide of rapamycin are organized into three multienzymes, RapA, RapB, and RapC, which contain a total of 14 modules (figure 1). The three multienzymes are organized such that the first four modules of polyketide chain elongation are in RapA, the following six modules for continued elongation are in RapB, and the final four modules to complete the biosynthesis of the linear polyketide are in RapC. Then, the linear polyketide is modified by the NRPS, RapP, which attaches L-pipecolate to the terminal end of the polyketide, and then cyclizes the molecule, yielding the unbound product, prerapamycin. The core macrocycle, prerapamycin (figure 2), is then modified (figure 3) by an additional five enzymes, which lead to the final product, rapamycin. First, the core macrocycle is modified by RapI, SAM-dependent O-methyltransferase (MTase), which O-methylates at C39.
Patients must be between 18 and 70 years old, have renal biopsy findings consistent with IgA nephropathy, have been treated with an Angiotensin Converting Enzyme inhibitor (ACEi) and/or an Angiotensin II Receptor Blocker (ARB) for at least 90 days at the maximum approved dose, have a proteinuria > 1 gm/day at diagnosis of IgA nephropathy and a level > 0.5 gm/day at the second screening visit, and a blood pressure controlled to ≤ 1302/80 with angiotensin blockade. Eligible candidates cannot have recently used cyclophosphamide, mycophenolate mofetil, azathioprine, Rituximab, or > 15 mg/day of prednisone or any other corticosteroid equivalent. The study investigates whether fostamatinib is a safe and effective treatment for IgAN. It is a Phase 2, multi-center, randomized, double-blind, ascending-dose, placebo-controlled clinical study. Primary outcome measures include the mean change in proteinuria as measured by spot urine protein/creatinine ratio (sPCR). Effects were evaluated for 100 mg, 150 mg, and placebo formulations taken twice daily by mouth for 24 weeks. The study began in October 2014 and is expected to complete by June 2017. History
Fostamatinib was approved for medical use in the United States in April 2018.The U.S. Food and Drug Administration (FDA) approved fostamatinib based on evidence from two identical, double-blind, placebo-controlled clinical trials, FIT-1 (NCT02076399) and FIT-2 (NCT02076412) of 150 adults with persistent or chronic ITP who had an insufficient response to previous treatment, which included corticosteroids, immunoglobulins, splenectomy, and/or a thrombopoietin receptor agonist. Participants were allowed to continue previous ITP treatment during the trial.