Rapamycin

in vivo

Rapamycin (2.0 mg/kg; intraperitoneal injection; every other day; 28 days) alone has a moderate inhibitory effect. However, the combination of Metformin and Rapamycin exerts a significantly increased inhibition of tumor growth compared with the control group, the Rapamycin monotherapy group and the Metformin monotherapy group.

Indications and Usage

Rapamycin (Rapa, or Sirolimus) is a new form of macrolide immunosuppressive agent. It is a white solid crystal. Its melting point is 183-185℃ and it is lipophilic. It is soluble in methanol, ethanol, acetone, chloroform, and other organic solvents, very slightly soluble in water, and almost insoluble in ether. It was first discovered in 1975 on the Chilean Easter Island as a secondary metabolite secreted by soil Streptomyces, and its chemical structure is that of a three-polyene macrolide compound. Rapamycin is a new form of immunosuppressive agent with good curative effects, low toxicity, and no nephrotoxicity. It can be used to maintain the immunity of transplant organs (especially in kidney transplants) to alleviate immunological rejections after organ transplant surgeries. The latest research has shown that Rapamycin can also be used to treat Alzheimer’s. When used on afflicted lab rats, it had a memory-restoring effect. Rapamycin oral tablets can be taken with grapefruit juice to treat melanoma (a type of benign tumor common among Western populations), dramatically increase other chemotherapy drugs’ anticancer effects, and extend patient survival. Rapamycin is a mammalian target of rapamycin (mTOR) targeting inhibitor, which can treat tumors that are related to this pathway including kidney cancer, lymphoma, lung cancer, liver cancer, breast cancer, neuroendocrine carcinoma, gastric cancer, etc. Its curative effects are especially strong for the rare diseases LAM (lymphangiomyomatosis) and TSC (tuberous sclerosis).

Mechanisms of Action

Rapamycin is a type of macrolide antibiotic and has a similar structure to Prograf (FK506), but has very different immunosuppressing mechanisms. FK506 suppresses T lymph cells from proliferating from G0 to G1 stage, while RAPA uses different cytokine receptors to block signal transduction, thus preventing T lymph cells and other cells from proliferating from G1 to S stage. Compared to Prograf, Rapamycin can block the signal transduction pathways of the calcium dependency and calcium non-dependency of T lymph cells and B lymph cells.

Adverse reactions

Rapamycin has similar side effects to those of Prograf. Many clinical trials have found that its side effects are dose dependent and reversible. A treatment dosage of Rapamycin has not been found to lead to any significant nephrotoxicity or gingival hyperplasia. Its main toxic side effects include: headache, nausea, dizziness, nosebleed, and join pain. Laboratory inspections for anomalies found: thrombocytopenia, decreased white blood cells, decreased hemoglobin, hypertriglyceridemia, hypercholesterolemia, hyperglycemia, increased liver enzymes (SGOT, SGPT), increased lactate dehydrogenase, hypokalemia, hypokalemia, etc. Rapamycin may lead to puffiness of eyelids and lead to lowered plasma phosphate levels. Similar to other immunosuppressants, Rapamycin may also increase the chance of infection, with reports of increased tendency towards pneumonia.

Indications

Mechanistic target of rapamycin (mTOR) is a serine/threonine-specific protein kinase in the PI3/PI4-kinase family. mTOR was named after the natural macrolide rapamycin, also known as sirolimus, which was isolated from a soil sample from Easter Island in the 1970s and later evaluated as an immunosuppressive agent. The anticancer activity of rapamycin was discovered in the 1980s, although the mechanismof action and the identification of the rapamycin target, mTOR, were not elucidated until the 1990s. Rapamycin and its macrocyclic analogues, such as temsirolimus (Torisel(R), Wyeth/Pfizer) and everolimus (Afinitor(R), Novartis), are grouped as “rapalogs” that constitute the first-generation mTOR inhibitors. Rapamycin was approved by the US FDA in 1999 as an immunosuppressive agent to prevent organ rejection in patients receiving kidney transplants. Although a large number of clinical studies have been performed to evaluate the anticancer activities of sirolimus in different types of cancers, such as invasive bladder cancer, breast cancer, and leukemia, most studies show limited efficacy. Outside oncological indications, sirolimus was approved by FDA for the treatment of a rare progressive lung disease lymphangioleiomyomatosis in 2015. Temsirolimus was approved for the treatment of advanced RCC. Everolimus was approved in the EU for the prevention of organ rejection in heart and kidney transplant recipients before FDA approved it in 2009 for the treatment of advanced RCC resistant to sunitinib or sorafenib and for the treatment of advanced or metastatic gastrointestinal and lung tumors in 2016. Additionally, rapamycin and rapalogs are being investigated as antiaging therapeutics or for the treatment of age-related diseases. Studies have revealed that mTOR activity can be retained under hypoxic conditions via mutations in the PI3K pathway, leading to increased translation and hypoxic gene expression and tumor progression.

Manufacturing Process

Streptomyces hygroscopicus NRRL 5491 was grown and maintained on oatmeal-tomato paste agar slants (T. G. Pridham et al.; Antibiotic Annual 1956-1957, Medical Encyclopedia Inc., New York, p. 947) and in Roux bottles containing the same medium. Good growth was obtained after 7 days of incubation at 28°C. Spores from one Roux bottle were washed off and suspended into 50 ml of sterile distilled water. This suspension was used to inoculate the first stage inoculum.The first-stage inoculum medium consisted of Emerson broth [R. L. Emerson et al., J. Bacteriol, 52, 357 (1946)] 0.4% peptone, 0.4% sodium chloride, 0.25% yeast extract and 1% glucose; pH 7.0; flasks containing the above medium were inoculated with 1 % of the spore suspension described above. The inoculated flasks were incubated for 30 hours at 28°C on a reciprocating shaker set at 65 r.p.m. (4 inch stroke).Production stageThe production stage was run in 250-liter New Brunswick fermenters Model F- 250, equipped with automatic antifoam addition system and pH recordercontroller. The fermenters were charged with 160 L of an aqueous production medium consisting of the following constituents: 1.0% soluble starch; 0.5% (NH4)2SO4; 0.5% K2HPO4; 1.5% glucose (Cerelose); 0.025% MgSO4; 0.005% ZnSO4; 0.001% MnSO4; 0.002% FeSO47H2O; 0.2% CaCO3; 0.5% "Blackstrap" molasses; 0.5% hydrolyzed casein; 0.2% lard oil; pH 7.1 to 7.3 of first stage inoculum. Incubation temperature: 28°C; aeration: 0.5 vol/vol/min; agitation: 250 r.p.m. The fermenters were sterilized at 121°C for 45 min, cooled and inoculated with one flask inoculum).A titre of ca. 20 μg/ml, determined by microbiological assay on agar plates seeded with Candida albicans, was reached in 5 days. The fermentation was stopped. The fermentation mixture was extracted twice with 1 v/v of nbutanol. The combined butanol extracts were washed with 1 v/v of water, dried with anhydrous sodium sulfate and evaporated to dryness under reduced pressure to yield a residue. The oily residue was extracted 3 times with 2 L of methanol. The combined methanol extracts were passed through diatomaceous earth (Celite) and evaporated to dryness to yield an oily residue containing crude Rapamycin.

Therapeutic Function

Immunosuppressive, Antifungal

Biological Activity

Antifungal and immunosuppressant. Specific inhibitor of mTOR (mammalian target of Rapamycin). Complexes with FKBP-12 and binds mTOR inhibiting its activity. Inhibits interleukin-2-induced phosphorylation and activation of p70 S6 kinase.

Biochem/physiol Actions

Rapamycin is a macrocyclic triene antibiotic possessing potent immunosuppressant and anticancer activity. It forms a complex with FKBP12 that binds to and inhibits the molecular target of rapamycin (mTOR). mTOR is a member of the phosphoinositide kinase-related kinase (PIKK) family that enhances cellular proliferation via the phosphoinositol 3-kinase/Akt signaling pathway. Inhibition of this pathway by rapamycin blocks downstream elements that result in cell cycle arrest in G1. The effectors of mTOR action include 4EBP1 and S6K1.

in vitro

Rapamycin (12.5-100 nM; 24 hours) treatment exerts modest inhibitory effect on lung cancer cell proliferation in a dose-dependent manner in all cell lines (A549, SPC-A-1, 95D and NCI-H446 cells) tested, achieving about 30-40% reduction in cell proliferation at 100 nM vs. ~10% reduction at 12.5 nM. Lung cancer cell line 95D cells are exposed to Rapamycin (10 nM, 20 nM) and RP-56976 (1 nM, 10 nM) alone or in combination (Rapamycin 20 nM+ RP-56976 10 nM). After 24 hours exposure to Rapamycin or RP-56976 alone does not significantly alter the level of expression or phosphorylation of ERK1/2, whereas cells treated with the combination of Rapamycin with RP-56976 exhibit a marked reduction in the phosphorylation levels of ERK1/2.

Drug interactions

Potentially hazardous interactions with other drugs Antibacterials: concentration increased by clarithromycin - avoid; concentration of both drugs increased with erythromycin; concentration reduced by rifampicin and rifabutin - avoid. Antifungals: concentration increased by itraconazole, fluconazole, ketoconazole, micafungin, miconazole,posaconazole and voriconazole - avoid with itraconazole, ketoconazole and voriconazole. Antivirals: concentration possibly increased by atazanavir, boceprevir and lopinavir; concentration of both drugs increased with telaprevir, reduce dose of sirolimus; concomitant use with dasabuvir plus ombitasvir/paritaprevir/ritonavir is not recommended unless the benefits outweigh the risks, if used together administer sirolimus 0.2 mg twice a week (every 3 or 4 days on the same two days each week). Sirolimus blood concentrations should be monitored every 4-7 days until 3 consecutive trough levels have shown stable concentrations of sirolimus. Sirolimus dose and/or dosing frequency should be adjusted as needed. Calcium-channel blockers: concentration increased by diltiazem; concentration of both drugs increased with verapamil. Ciclosporin: increased absorption of sirolimus - give sirolimus 4 hours after ciclosporin; sirolimus concentration increased; long-term concomitant administration may be associated with deterioration in renal function. Cytotoxics: use crizotinib with caution. Grapefruit juice: concentration of sirolimus increased - avoid. Mycophenolate: concomitant use of mycophenolate and sirolimus increases plasma levels of both sirolimus and mycophenolic acid.

Metabolism

Sirolimus is metabolised by the cytochrome P450 isoenzyme CYP3A4. Metabolism occurs by demethylation or hydroxylation, and the majority of a dose is excreted via the faeces.

Immunosuppression in Organ Transplantation

Sirolimus is used for the prophylaxis of renal graft rejection in organ transplantation. Its potent immunosuppressive activity and unique mechanism of action make it valuable in preventing rejection reactions.

Treatment of Vascular Anomalies

Sirolimus shows promising results in the management of vascular anomalies, particularly vascular tumors associated with life-threatening coagulopathy and venous and lymphatic malformations. It inhibits the mammalian target of rapamycin (mTOR), which plays a crucial role in cellular processes involved in vascular anomalies.

Treatment of Lymphatic Malformations (LM) and Lymphangioleiomyomatosis (LAM)

Sirolimus has been approved for the treatment of lymphangioleiomyomatosis (LAM), a rare disease characterized by progressive lung disease. It has also been used to treat lymphatic malformations (LM) in various body areas, showing potential to improve symptoms and reduce the size of the malformations.

Antifungal Activity

Sirolimus was initially isolated as an antifungal agent with potent activity against Candida. However, its subsequent discovery of antitumor and immunosuppressive activities led to its exploration in various medical applications beyond antifungal therapy.

Induction of Fetal Hemoglobin (HbF) in 尾-Thalassemia Patients

Sirolimus serves as a strong inducer of fetal hemoglobin (HbF) in 尾-thalassemia patients, as demonstrated in vitro and in vivo studies. This property suggests its potential role in the management of 尾-thalassemia.

description

Rapamycin (also known as Sirolimus) is macrocyclic lactone produced by the bacterium Streptomyces hygroscopicus isolated from soil samples from Easter Island. Rapamycin is an antifungal agent with immunosuppressive properties. Rapamycin has antirejection properties without the side effects associated with other antirejection agents. Rapamycin binds to a specific protein, Target of Rapamycin (TOR). TOR is serine/threonine kinase. TOR (mTOR) forms two major complexes: mTORC1,and mTORC2. The mTORC1 consists of mTOR, Raptor, mLST8, FKBP38, PRAS40, and Deptor, and through specific binding of rapamycin to FKBP12, rapamycin inhibits the activity of mTORC1 leading to a decrease in protein synthesis, increased autophagy and inhibition of cell growth.

Application

As an mTOR inhibitor, sirolimus has a broad spectrum of activity that has demonstrated the ability to inhibit inflammation, proliferation, angiogenesis, fibrosis, and hyperpermeability. Sirolimus currently has multiple uses in the prevention of rejection in organ transplantation and, recently, in the treatment of advanced renal cell carcinoma. Sirolimus-eluting cardiac stents have been shown to limit the rate of overgrowth of tissue and thus prevent coronary restenosis. Early studies suggest that it may be an effective agent for controlling severe uveitis and that it may also have a role in treating agerelated macular degeneration.

Definition

ChEBI: A macrolide isolated from Streptomyces hygroscopicus consisting of a 29-membered ring containing 4 trans double bonds, three of which are conjugated. It is an antibiotic, immunosupressive and antineoplastic agent.

Brand name

Rapamune (Wyeth).

General Description

Rapamycin is an anti-fungal antibiotic isolated from Streptomyces hygroscopicus. This antibiotic is active against all strains of Candida albicans. It blocks the signal transduction pathways required for the activation of T-helper cells.