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. Next, a carbonyl is installed at C9 by RapJ, a cytochrome P-450 monooxygenases (P-450). Then, RapM, another MTase, O-methylates at C16. Finally, RapN, another P-450, installs a hydroxyl at C27 immediately followed by O-methylation by Rap Q, a distinct MTase, at C27 to yield rapamycin. 
However, despite its rigor, this study is problematic in that only 12 patients are included. Also, what happens to these patients after six months? Even more importantly, the study does not address the cost of the eluting stents, which are $700 per side. In most cases, eluting stents are not covered by insurance, and their use can become a financial burden for patients. Further, nasal polyps and associated chronic rhinosinusitis are lifelong problems. Are these stents meant to be used over and over again? If so, compared with other methods of treatment, stent use may not be cost effective.