Doravirine (MK-1439) is a nonnucleoside inhibitor of HIV reverse transcriptase (NNRTI). It displays excellent activities against not only WT viruses but also a broader panel of NNRTI-resistant viruses. Doravirine is a prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the treatment of HIV infection in adults who have never taken HIV medicines before. Doravirine is always used in combination with other HIV medicines.

Segesterone acetate (elcometrine), a progestin, is sold in combination with ethinyl estradiol under the brand name Annovera. Annovera is indicated for use by females of reproductive potential to prevent pregnancy. Segesterone acetate acts as an agonist of the progesterone receptor and it doesn’t possess estrogenic, androgenic, antiandrogenic, or antimineralocorticoid activity.

Niraparib (MK-4827) displays excellent PARP 1 and 2 inhibition. Inhibition of PARP in the context of defects in other DNA repair mechanisms provide a tumor specific way to kill cancer cells. Niraparib is in development with TESARO, under licence from Merck & Co, for the treatment of cancers (ovarian, fallopian tube and peritoneal cancer, breast cancer, prostate cancer and Ewing's sarcoma). Niraparib was characterized in a number of preclinical models before moving to phase I clinical trials, where it showed excellent human pharmacokinetics suitable for once a day oral dosing, achieved its pharmacodynamic target for PARP inhibition, and had promising activity in cancer patients. It is currently being tested in phase 3 clinical trials as maintenance therapy in ovarian cancer and as a treatment for breast cancer.

Elbasvir is an inhibitor of the Hepatitis C Virus (HCV) Non-Structural protein 5A (NS5A). Elbasvir was approved by the FDA in January 2016 for the treatment of hepatitis C. It was developed by Merck and completed Phase III trials, used in combination with the NS3/4A protease inhibitor grazoprevir under the trade name Zepatier. Zepatier is indicated for treatment of chronic HCV genotype 1 or 4 infection in adults.

Grazoprevir is a second generation NS3/4A protease inhibitor approved in the EU and the USA for the treatment of hepatitis C virus (HCV) genotypes 1 and 4 infections in adult patients in combination with elbasvir (C virus (HCV) NS5A inhibitor) as the fixed-dose combination product Zepatier with or without ribavirin. In phase III trials, 12 or 16 weeks of treatment with once-daily elbasvir/grazoprevir (fixed-dose tablet or as individual agents), taken with or without ribavirin, generally provided high rates of sustained virological response at 12 weeks (SVR12) in treatment-naive and -experienced adult patients with chronic HCV genotype 1a, 1b or 4 infection, including those with or without compensated cirrhosis, HIV co-infection, inherited blood disorders or chronic kidney disease or patients receiving opioid agonist therapy or of Japanese origin. Elbasvir/grazoprevir was generally well tolerated. Thus, elbasvir/grazoprevir, with or without ribavirin, represents an effective new option for the treatment of adults with chronic HCV genotype 1 and 4 infection, including a number of difficult-to-treat populations.

Vilazodone is a serotonergic antidepressant. The mechanism of the antidepressant effect of vilazodone is not fully understood but is thought to be related to its inhancement of serotonergic activity in the CNS through selective inhibition of serotonin reuptake. Vilazodone is also a partial agonist at serotonergic 5-HT1A receptors; however, the net result of this action on serotonergic transmission and its role in vilazodone’s antidepressant effect are unknown. The side effects include activation of mania/hypomania in patients with bipolar disorder, seizures can occur with treatment in patients with a seizure disorder.

Raltegravir (RAL, Isentress, formerly MK-0518) is an antiretroviral drug produced by Merck & Co., used to treat HIV and it is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection in patients 4 weeks of age and older. Raltegravir inhibits the catalytic activity of HIV-1 integrase, an HIV-1 encoded enzyme that is required r viral replication. Inhibition of integrase prevents the covalent insertion, or integration, of unintegrated linear HIV-1 DNA into the host cell genome preventing the formation of the HIV-1 provirus. The provirus is required to direct the production of progeny virus, so inhibiting integration prevents propagation of the viral infection. Raltegravir did not significantly inhibit human phosphoryl transferases including DNA polymerases α, β, and γ. Coadministration with others drugs that are strong inducers of UGT1A1, such as rifampin, may result in reduced plasma concentrations of raltegravir. The most common adverse reactions of moderate to severe intensity (≥2%) are insomnia, headache, dizziness, nausea and fatigue. Severe, potentially life-threatening, and fatal skin reactions have been reported. This include cases of Stevens-Johnson syndrome and toxic epidermal necrolysis. Hypersensitivity reactions have also been reported and were characterized by rash, constitutional findings, and sometimes, organ dysfunction, including hepatic failure. The major mechanism of clearance of raltegravir in humans is UGT1A1-mediated glucuronidation.

Sitagliptin (MK-0431), chemically (2R)-4-Oxo-4-[3- (trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin- 7(8H)-yl]-1-(2,4,5-trifl uorophenyl)butan-2-amine has a very high selectivity towards DPP-4, with an IC(50) of 18 nM. There is no affinity towards other DDP enzymes (DPP- 8 and DPP-9). It has been approved for the treatment of type 2 diabetes in the USA and Europe and is registered by the name Januvia (Merck Pharmaceuticals, Whitehouse Station, NJ, USA). In healthy volunteers and in patients with type 2 diabetes of different ethnic background, the tolerability of different doses given once or twice daily is good. The drug works to competitively inhibit a protein/enzyme, dipeptidyl peptidase 4 (DPP-4), that results in an increased amount of active incretins (GLP-1 and GIP), reduced amount of release of glucagon (diminishes its release) and increased release of insulin. Sitagliptin is an incretin enhancer and the first marketed medication belonging to the gliptin class. In fact, no published literature exists regarding incidence or severity of hypoglycemia when sitagliptin is used off-label in combined with insulin therapy. However, is recommended to use methods to avoid hypoglycemia when using this off-label combination. Approximately 79% of sitagliptin is excreted unchanged in the urine with metabolism being a minor pathway of elimination. Elimination of sitagliptin occurs primarily via renal excretion and involves active tubular secretion. Sitagliptin is a substrate for human organic anion transporter-3 (hOAT-3), which may be involved in the renal elimination of sitagliptin

Aprepitant (brand name: Emend (the brand name used in all English-speaking countries an antiemetic, is a substance P/neurokinin 1 (NK1) receptor antagonist which, in combination with other antiemetic agents, is indicated for the prevention of acute and delayed nausea and vomiting associated with initial and repeat courses of highly emetogenic cancer chemotherapy. Aprepitant has little or no affinity for serotonin (5-HT3), dopamine, and corticosteroid receptors, the targets of existing therapies for chemotherapy-induced nausea and vomiting. Aprepitant has been shown to inhibit emesis induced by cytotoxic chemotherapeutic agents, such as cisplatin, via central actions. Animal and human Positron Emission Tomography (PET) studies with aprepitant have shown that it crosses the blood brain barrier and occupies brain NK1 receptors.

Tirofiban is a non-peptide antagonist of the platelet glycoprotein (GP) IIb/IIIa receptor. Tirofiban is a reversible, competitive inhibitor of GP IIb/IIIa receptors, exerting its effects via the prevention of the binding of fibrinogen and other ligands, resulting in the inhibition of the last common step of thrombi formation. Tirofiban was discovered by Merck, USA, and was approved by the FDA in 1998 under the trade name AGGRASTAT. AGGRASTAT, in combination with heparin, is indicated for the treatment of acute coronary syndrome, including patients who are to be managed medically and those undergoing percutaneous transluminal coronary angioplasty or atherectomy. AGGRASTAT reduces the risk of ischaemic complications in patients with unstable angina/non-Q-wave myocardial infarction and high-risk patients undergoing revascularisation when used against a background of heparin and aspirin. Furthermore, the drug has an acceptable tolerability profile. Therefore, intravenous tirofiban is likely to be used as an adjunct to heparin and aspirin in patients with acute coronary syndromes including high-risk patients undergoing revascularisation.