Other studies suggest continued immunological and clinical benefits if the HIV RNA level is maintained <10 000–20 000 copies/mL [66]. Continuing or commencing NRTIs, even in the presence of known resistance may contribute partial ARV activity [54, 55]. Hence, if the CD4 cell count is well maintained (>200 cells/μL), it may be better to continue the failing regimen and not change treatment until investigational agents are available that can be put together with drugs, which may have only partial activity

at best, to increase the likelihood of constructing virologically suppressive and durable regimen options. In general, GSK-3 activity adding a single, fully active ARV to a failing regimen is not recommended because of the risk of rapid development of resistance. However, in patients with a high likelihood of clinical progression (e.g. CD4 cell count <100 cells/mL) and limited drug options, adding a single drug may reduce the risk of immediate clinical

progression, because even transient decreases in HIV RNA and/or transient increases in CD4 cell counts have been associated with clinical benefits [67]. Potential benefits must be balanced with the ongoing risk of accumulating additional resistance mutations and patients should maintain that regimen for the shortest period possible [68, 69]. Where feasible, patients should be given the opportunity to enrol in research studies or expanded access programmes evaluating investigational new drugs. Some drugs are likely to be available in the near future that might be find protocol sequenced in the same class (e.g. dolutegravir) although others with novel sites of action (e.g. maturation ADAMTS5 inhibitors, CD4 receptor antagonists, etc.) are still in earlier phases of development and some years off randomized trials. Drugs developed

for, and used in, other settings such as pegylated interferon that have been incidentally demonstrated to decrease VL should not be used without discussion with an experienced HIV physician as data are either too limited or contradictory. Several studies and an early meta-analysis suggested that CCR5 receptor antagonists were associated with significant gains in CD4 cell counts even in the presence of C-X-C chemokine receptor type 4 tropic virus. However, a more recent meta-analysis refuted this finding (P=0.22) when comparing with other new drugs [53]. A priority question that the Writing Group addressed was whether 3TC/FTC should be used in maintaining an RT mutation at codon 184 in patients with limited or no therapeutic options. Although the M184V mutation is associated with resistance to 3TC/FTC, the mutation has a broad influence on the RT enzyme. In vitro studies have shown that M184V-possessing enzymes have lower processivity and higher fidelity and replicate more slowly than WT enzymes [70].