Rilpivirine (TMC278) matches efavirenz in phase 3 studies, with fewer side-effects

Images from presentation by Dr Cal Cohen of Community Research Initiative New England (www.crine.org)
This article is more than 9 years old. Click here for more recent articles on this topic

The new Tibotec non-nucleoside reverse transcriptase inhibitor rilpivirine (TMC278) is just as effective as efavirenz in suppressing viral load, but less likely to cause side-effects, delegates heard today at the Eighteenth International AIDS Conference in Vienna.

Rilpivirine is likely to be submitted for licensing in the United States very quickly, and will also be combined in a once-daily tablet with Gilead’s drugs tenofovir and emtricitabine.

Dr Cal Cohen of Community Research Initiative New England, Boston, presented a pooled analysis of two international phase III studies, ECHO and THRIVE, which randomised nearly 1400 people with HIV with no previous experience of treatment to receive either rilpivirine 25mg once daily or efavirenz 600mg once daily in combination with two nucleoside analogues.

Glossary

nucleoside

A precursor to a building block of DNA or RNA. Nucleosides must be chemically changed into nucleotides before they can be used to make DNA or RNA. 

p-value

The result of a statistical test which tells us whether the results of a study are likely to be due to chance and would not be confirmed if the study was repeated. All p-values are between 0 and 1; the most reliable studies have p-values very close to 0. A p-value of 0.001 means that there is a 1 in 1000 probability that the results are due to chance and do not reflect a real difference. A p-value of 0.05 means there is a 1 in 20 probability that the results are due to chance. When a p-value is 0.05 or below, the result is considered to be ‘statistically significant’. Confidence intervals give similar information to p-values but are easier to interpret. 

log

Short for logarithm, a scale of measurement often used when describing viral load. A one log change is a ten-fold change, such as from 100 to 10. A two-log change is a one hundred-fold change, such as from 1,000 to 10.

central nervous system (CNS)

The brain and spinal cord. CNS side-effects refer to mood changes, anxiety, dizzyness, sleep disturbance, impact on mental health, etc.

reverse transcriptase

A retroviral enzyme which converts genetic material from RNA into DNA, an essential step in the lifecycle of HIV. Several classes of anti-HIV drugs interfere with this stage of HIV’s life cycle: nucleoside reverse transcriptase inhibitors and nucleotide reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs). 

The ECHO study randomised 690 patients, and all received a nucleoside analogue backbone of tenofovir and emtricitabine. THRIVE randomised 678 patients, and the nucleoside backbone was chosen by the patient’s doctor. Around 60% of participants received tenofovir/FTC and 30% received AZT/3TC and 10% received abacavir/3TC.

Participants had relatively low CD4 counts (a median of around 250), and high viral load (median 5 log, or 100,000 copies/ml).

After 48 weeks of treatment the proportions with viral load below 50 copies/ml were almost identical (84.3% in the rilpivirine arm, 82.3% in the efavirenz arm), a non –inferior outcome.

Virological failures, defined as two viral loads above 50 copies/ml even if viral load was suppressed again at week 48) were more frequent in the rilpivirine arm (9% vs 4.8%), and this difference was largely driven by the higher failure rate in the ECHO study (11% vs 4.4%), in which patients received a variety of nucleoside backbones. The statistical significance of this difference was not reported.

Commenting on this difference, Cal Cohen said that there was no difference in response rates according to nucleoside backbone, nor by baseline viral load

In patients who experienced virological failure, different primary resistance mutations occurred; while efavirenz-treated patients developed the K103N mutation, rilpivirine-treated patients tended to develop the E138K mutation that causes resistance to the second-line NNRTI etravirine. Half of those who failed rilpivirine developed resistance to the drug, and of them, 90% were resistant to etravirine too.

Discontinuations due to adverse events were significantly more common in the efavirenz group (6.7% vs 2%) (p=0.005), and central nervous system adverse events (such as dizziness and abnormal dreams were significantly more common in the efvairenz, occurring two to three times more often in these patients (overall frequency 38% vs 17%). Rash was also more common in efavirenz-treated patients.

Further information

View abstracts and slides from this session on the official conference website.

References

Cohen C et al. Pooled week 48 efficacy and safety results from ECHO and THRIVE, two double-blind, randomised phase III trials comparing TMC278 versus efavirenz in treatment-naïve HIV-1-infected patients. Eighteenth International AIDS Conference, Vienna, abstract THLBB206, 2010.