Etravirine (Intelence)

Etravirine (Intelence) is an anti-HIV drug that reduces the amount of virus in the body and belongs to the class of drugs known as non-nucleoside reverse transcriptase inhibitors (NNRTIs). NNRTIs stop the activity of HIV’s reverse transcriptase enzyme, which is needed to copy the genetic code of HIV into a form that can be inserted into human cells. 

Formerly known as TMC-125, etravirine was developed by Tibotec Pharmaceuticals, Ltd. and is a diarylpyrimidine (DAPY), a different type of NNRTI specifically designed to be less susceptible than other NNRTIs to resistance mutations. As a flexible molecule, it can fit into different shaped binding pockets in the reverse transcriptase enzyme and this is why it remains active against HIV that is resistant to other NNRTIs. (Das)

Etravirine is indicated for treatment-experienced adults who have evidence of viral replication and HIV strains resistant to an NNRTI and other antiretrovirals. It should not be combined with licensed nucleoside analogues alone, due to the risk of virologic failure.

Etravirine is not recommended for use with an unboosted protease inhibitor, ritonavir-boosted atazanavir, fosamprenavir, or tipranavir. In addition, the manufacturer recommends resistance testing before initiating therapy with this drug.

Etravirine was approved in the US and European Union in 2008. Etravirine is marketed by Janssen, a subsidiary of Johnson & Johnson.

Effectiveness

Studies that led to the approval of etravirine showed that when combined with darunavir/ritonavir plus at least two nucleoside analogues selected by resistance testing, etravirine was significantly more effective than placebo in suppressing viral load in treatment-experienced people with at least one NNRTI resistance mutation and three or more primary protease inhibitor mutations. (Katlama) A subsequent study showed that etravirine was more effective in treatment-experienced people with fewer than three NNRTI mutations. (TMC125-C223 Writing Group)

Despite its impressive activity against NNRTI-resistant HIV, those findings showed that the more NNRTI resistance mutations a person has, the lower the viral load reduction. Individuals with no NNRTI resistance mutations at baseline had a median viral load reduction of nearly 3 logs (99.9%) after 34 weeks of etravirine treatment combined with an optimised background regimen. Those with three or more NNRTI mutations had a viral load reduction of less than one log (90%).

Taking it

The recommended oral dose of etravirine tablets is 200mg (two 100mg tablets) twice daily following a meal. Taking the drug on an empty stomach is not advised. For those who have difficulty swallowing, etravirine can be dissolved in water.

Side effects

The common side effects of etravirine are rash, headache, peripheral neuropathy (damage to nerves in the hands or feet, causing tingling or numbness), blurred vision, tiredness, difficulty in sleeping, anxiety, changes in taste, diarrhoea, nausea, vomiting, indigestion and acid reflux, dry mouth, dry skin, itching, flatulence, abdominal pain, constipation, kidney failure, heart attack, shortness of breath, night sweats,

Raised blood sugar, triglyceride or cholesterol levels, anaemia, low platelet counts, high blood pressure, raised liver enzymes, raised amylase and lipase levels are commonly observed in people taking etravirine.

Mild to moderate rash is the most common side effect of etravirine. Women are more likely to develop a rash than men. The rash usually appears 1-2 weeks after starting treatment and normally clears up within two weeks.

Rarely, etravirine can cause a hypersensitivity (allergic) reaction. If you develop a rash with other symptoms, such as a fever, blisters or swelling, seek medical advice.

Severe rash with symptoms is either toxic epidermal necrolysis (TEN) or drug rash with eosinophilia and systemic symptoms (DRESS).

These reactions develop between three and six weeks after treatment with the drug is started. In most cases, they disappear when treatment with etravirine  is stopped and therapy with corticosteroids is provided. Symptoms include rash, fever, general malaise, fatigue, muscle or joint aches, blisters, oral lesions, conjunctivitis, hepatitis, and high concentrations of a type of blood cell calls eosinophils. In phase III studies of etravirine severe rash occurred in 1.3% of people and 2% had to stop taking the drug due to serious rash.

If a hypersensitivity reaction to the drug is diagnosed, treatment with it should be stopped immediately. People who have stopped treatment due to hypersensitivity reactions should not restart therapy. 

Resistance

In contrast to other NNRTIs, more than one resistance mutation needs to develop, in order to bring about resistance to etravirine. (Brillant) (Vingerhoets) The presence of the most common NNRTI mutation, K103N, did not affect the treatment response in individuals on etravirine in the DUET studies; however, the presence at baseline of V179D, V179F, V179T, Y181V, or G190S was associated with a decreased virologic response to etravirine. (Madruga) (Lazzarin)

Tibotec, which developed etravirine, noted that cross-resistance to efavirenz and/or nevirapine is to be expected after virologic failure while on an etravirine-containing regimen.

Drug interactions

Interactions with protease inhibitors complicate regimens containing etravirine. This is an especially important issue for a second-line NNRTI that may be used in third-line regimens with protease inhibitors.

Etravirine cannot be co-administered with boosted tipranavir/ritonavir (Aptivus), atazanavir/cobicistat (Evotaz), darunavir/cobicistat (in Rezolsta or Symtuza), full-dose ritonavir (Norvir 600mg), unboosted protease inhibitors, or other NNRTIs.

Because etravirine is such a potent inducer of the cytochrome p450 CYP3A4 pathway, it greatly speeds up the metabolism of the CCR5 antagonist maraviroc (Celsentri, Selzentry). Co-administration can reduce total maraviroc concentrations over a 12-hour period by 53% (AUC₁₂) and peak levels of maraviroc (C_max) by 60%.

Therefore, if an individual isn't also taking a potent CYP3A4 inhibitor such as a protease inhibitor, the recommended clinical dose for maraviroc alongside etravirine is 600mg twice daily. However, if maraviroc is being dosed alongside etravirine and darunavir together, a dose reduction to 150mg twice daily is necessary. Data showed no effect of maraviroc on etravirine pharmacokinetics, so no dose adjustment of etravirine is necessary.

Etravirine should only be used with dolutegravir if combined with atazanavir/ritonavir, darunavir/ritonavir, or lopinavir/ritonavir.

Etravirine cannot be given with carbamazepine, phenobarbital, phenytoin, rifabutin (if part of a protease inhibitor/ritonavir containing-regimen), rifampicin, rifapentine, or St John's wort (Hypericum perforatum). It does not appear to affect blood levels of methadone. Etravirine may reduce levels of clopidogrel.

Etravirine should not be used alongside the hepatitis C direct-acting antivirals daclatasvir or elbasvir/grazoprevir (Zepatier).

Some drugs can interact with etravirine and change blood levels of one or both drugs, so dose adjustments may be needed. Drugs that this applies to include:

• amiodarone
• artemether/lumefantrine
• atorvastatin
• bepridil
• clarithromycin
• clopidogrel
• cyclosporine
• dexamethasone
• diazepam
• digoxin
• disopyramide
• flecainide
• fluvastatin
• lidocaine
• lovastatin
• mexiletine
• pravastatin
• propafenone
• quinidine
• rifabutin
• rosuvastatin
• sildenafil
• simvastatin
• sirolimus
• tacrolimus
• tadalafil
• vardenafil
• warfarin.

The efficacy of etravirine and/or its side effect profile can change when given with inhibitors, inducers, or substrates of CYP3A4, CYP2C9, and CYP2C19.

Children

Etravirine is approved for use in children of two years and over. When combined with an optimised background regimen and dosed either by weight (5.2mg/kg) or 200mg twice a day etravirine suppressed viral load below 50 copies/ml in 56% of 101 children and adolescents. (Tudor-Williams)

Pregnancy

Etravirine has received only minimal study in pregnant women.

Laboratory studies in animals suggest that the drug is safe during pregnancy, and a case series has been presented of five pregnant women who received the drug through compassionate access due to limited options. (Izurieta) Three of the women took therapy for their entire pregnancy, the other two during the third trimester only.

Monitoring of peak, trough and steady-state concentrations of etravirine showed that these were comparable to those seen in non-pregnant adults, suggested that no dose modification is necessary during pregnancy. None of their infants were infected with HIV. One infant was born with a minor abnormality to the right ear, but was healthy in all other respects. No birth abnormalities were observed in the other five babies.