Effects of Maraviroc (MVC) on HIV-related Kaposi's Sarcoma (KS)

Trial Information

Effects of Maraviroc (MVC) on HIV-related Kaposi's Sarcoma (KS)

Although the advent of antiretroviral therapy (ART) may have greatly decreased the incidence
of Kaposi's Sarcoma (KS) in resource rich settings, KS continues to be the most prevalent
AIDS-defining malignancy in the world and carries with it significant morbidity and
mortality[1]. Indeed, in a recent epidemiological study examining cancers in Kampala,
Uganda, KS was found to be second only to prostate cancer in terms of incidence rates[2].

There is growing evidence that CCR5 may be involved in the pathogenesis of KS. Kaposi's
Sarcoma-associated Herpes Virus (KSHV), an agent found as necessary for KS pathogenesis [10,
11], encodes viral macrophage inflammatory proteins or vMIP [7-9]. vMIP-I and vMIP-II have
been found to be ligands for chemokine receptors, and in particular the CCR5 receptor [5,
6], suggesting a potential role in the inflammatory process needed for KS pathogenesis.
Further, vMIP-I induces Ca(2+) mobilization in monocytes expressing CCR5, suggesting an
agonistic relationship between vMIP-I and the CCR5 receptor [4]. In addition, vMIP has been
found to be proangiogenic when expressed in endothelial cells, a key feature of KS tumor
survival [12]. As well, CCR5 has been found to be significantly increased in T cells
populations of KS patients (from a preliminary study), and in 2 double-blind,
placebo-controlled phase 3 studies in which a total of 1049 patients received the randomly
assigned drug MVC, there was a trend revealing a lower incidence of KS in MVC arms vs
placebo (0.36% vs 1.43%) [3]. This agonistic binding relationship between protein vMIP and
CCR5, the proangiogenic activity associated with vMIP, the increased expression of CCR5 in
KS, and trend towards lower incidence of KS when patients are taking MVC, suggest CCR5 may
play an important role in KS pathogenesis. This involvement of CCR5 in KS pathogenesis
implies that MVC may function as a potential therapeutic for KS. To date, there have been
no studies examining the effect of MVC on KS.

There is a need for therapeutic development for KS. Standard of care for KS involves
initiation or optimization of antiretroviral therapy. A significant proportion of KS cases
do not respond to ART alone, with non-response rates ranging from 25-55%, with response
times averaging 9 or more months depending on which patient series is identified [13, 14].
In severe or in cases of KS unresponsive to ART, standard of care involves systemic
chemotherapy with liposomal doxorubicin [15], which is not without adverse reactions.
Adverse reactions to liposomal doxorubicin include cardiac toxicity, nausea, vomiting,
diarrhea, abdominal pain, fatigue, and patients may require pre-regime tests of varying
costs, along with resources and time needed for intravenous infusion [16]. Nonresponse rates
for liposomal doxorubicin hover around 20% [15, 17]. Focal cases may be more amenable to
radiation therapy or intralesional velban [18, 19]. However, radiation and intralesional
therapies are limited to focal sites, require monitored visits and specialized care, can be
given only in limited amounts, and carry various adverse effects [18, 19]. With these
nonresponse rates, potential adverse reactions, and resources and time needed for
therapeutic delivery, there are clear benefits proferred by an effective oral therapy
requiring minimal monitoring, as is the case with MVC.

Maraviroc (MVC) is a member of a new class of antiretroviral compounds known as small
molecule CCR5 antagonists that block R5 HIV entry into CD4 cells. Maraviroc has demonstrated
selective and reversible binding to CCR5, as well as potent antiviral activity in vitro
against a wide range of laboratory adapted strains of R5 HIV from Clades A, B, C, D, E, F,
G, J and O. Maraviroc also retains in vitro antiviral activity against clinical isolates
resistant to the existing drug classes, but has no activity against viruses that enter CD4+
cells using CXCR4. In vitro studies with approved antiretroviral medications indicate that
there is no evidence of antagonism with any members of the other four classes of
antiretroviral medications; nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs),
non- nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs) or
fusion inhibitors.

Although there is growing evidence that CCR5, a potential therapeutic target, is involved in
KS pathogenesis [3-9], to date there are no studies examining the effects of a CCR5
inhibitor such as Maraviroc (MVC) on KS. As such, the aim of this study is to examine the
effect of Maraviroc, a CCR5 inhibitor, on KS.