ovarian cancer is the deadliest gynecological cancer , with 22,000 new cases and 15,000 deaths 
 anticipated within the united states in 2012.1 
 despite years of intense research , the etiology of this disease remains unknown . there is currently 
 no consistent early symptom or screening test , and consequently , most patients present with 
 advanced - stage disease . traditional therapy for ovarian cancer has included maximal cytoreductive 
 surgery followed by cytotoxic chemotherapy with a platinum / taxane - based regimen . while most ovarian 
 cancer is initially chemosensitive , recurrence of the disease is common and may be categorized as 
 either platinum - sensitive or refractory . current treatment regimens for platinum resistant 
 recurrence include single agent paclitaxel , liposomal doxorubicin , or topotecan . outcomes with these 
 regimens are poor , with significant potential toxicity , thus , new treatment modalities are needed . the gynecologic oncology group ( gog ) is actively pursuing alternative treatment regimens including 
 intraperitoneal chemotherapy , dose - dense paclitaxel , and anti - angiogenesis therapy . to date , there 
 have been four positive phase iii clinical trials demonstrating improved progression - free survival 
 with the anti - angiogenesis monoclonal antibody bevacizumab , in patients with ovarian cancer.25 additional research has focused on immunotherapy and includes:6 administration of tumor - directed antibodies,7,8 administration of 
 immune - stimulatory cytokines , 9,10 peptide cancer vaccines , adoptive cell 
 transfers,11 depletion of regulatory t cells , and 
 dysfunctional immune cosignaling blockade . further 
 insights were gained with the mapping of the ovarian cancer genome atlas,12 which elucidated multiple aberrant cellular pathways within ovarian 
 tumor cells . these discoveries have generated interest in specific pathway inhibition including : 
 poly ( adenosine diphosphate [ adp]-ribose ) polymerase ( parp ) inhibitors,13,14 
 anti - folic acid receptor inbitors,15 heat shock 
 protein 90 inhibition,16 gamma secretase 
 inhibitors,17 and aurora kinase inhibtors.18 however , tumors often possess multiple aberrant 
 pathways with a high degree of cross talk between signaling cascades , and thus , therapeutics 
 directed at pathway inhibition may not have optimal success if the complexity of the pathway is not 
 fully recognized or if a given patient does not possess the targeted aberrant pathway . reversing ovarian cancer tumors are known to contain tumor - infiltrating lymphocytes ( including 
 t cells and dendritic cells [ dcs ] ) . these lymphocytes , however , are quiescent and do 
 not readily attack tumor cells . the reason for this is multifactorial ; however , regulatory t cells 
 and inert dcs are postulated to play a role in the creation of this immunosuppression . activation of 
 toll - like receptors ( tlrs ) holds potential for the reversal of this immunosuppressive 
 microenvironment . as mentioned in the awarding of the 2011 nobel prize in medicine or physiology , 
 tlrs and dcs are the link between innate and adaptive immunity,19 thus , triggering the innate immune response in ovarian cancer tumors 
 may result in activation of cytotoxic t cells and natural killer cells and in the elimination of 
 ovarian cancer cells . ralph steinmann , bruce beutler , and jules hoffmann were awarded the 2011 nobel prize in medicine 
 or physiology for discovering the roles that dcs and tlrs play as the gatekeepers of innate 
 immunity . the innate immune system is the first line of defense against foreign organisms and 
 includes natural killer cells , mast cells , eosinophils , basophils , physical barriers , and phagocytic 
 cells , including dcs , macrophages , and neutrophils . dcs possess tlrs , which were the first 
 pathogen - associated pattern - recognition receptors to be discovered . activation of these receptors by 
 exposure to foreign molecules results in the activation of a signal cascade , with multiple 
 downstream effects.20 upon activation , dcs 
 increase their production of major histocompatibility complex ( mhc ) class ii molecules and migrate 
 to draining lymph nodes , where they present antigens to nave t cells . the presentation of 
 antigens via mhc class ii molecules to t helper cells type 1 and 2 results in the activation of the 
 adaptive immune response , with clonal expansion of t cells and the activation of b cell - mediated 
 antibody secretion . tumor - infiltrating lymphocytes were described in the microenvironment of ovarian cancer as early 
 as 1988.21 the types of lymphocytes present 
 include cd8 + t cells , macrophages , a relatively low concentration of natural killer cells , b 
 cells , polymorphonuclear cells , and rare mast cells.22 significantly , the presence of tumor - infiltrating lymphocytes is associated with improved 
 overall survival.23,24 however , these lymphocytes do not actively target ovarian cancer 
 cells . rather , an immunosuppressive microenvironment is present within the tumor . active evasion of 
 the immune response involves at least two cell types : ( 1 ) cd4 + cd25 + t cells ( t 
 regulatory cells [ tregs ] ) , and ( 2 ) cd11c + mch - ii myeloid dcs ( mdcs ) , which 
 are the most abundant subset of leukocytes in the solid ovarian cancer microenvironment.25 recent research has exploded regarding the role and 
 function of tregs6,7,24,2632 and suggests that tregs actively induce cytotoxic t cell anergy in at least two ways : ( 1 ) 
 direct cell - to - cell contact inhibition , and ( 2 ) humoral inhibition , including the downregulation of 
 interleukin-2 . the presence of tregs has been associated with poor prognosis . in one study , individuals with the highest treg counts per high - powered field of ovarian cancer tumor tissue had a 
 25-fold higher death hazard ratio ( 95% ci 6.892.1)33 compared with those with the lowest treg cell counts , even after 
 controlling for the stage of disease and surgical debulking . additionally , mdcs have recently been 
 shown to actively inhibit t cell antitumor activity by expressing functional levels of the 
 immunosuppressive proteins pd - l1.34 tlrs 
 constitute a family of highly conserved pattern - recognition receptors ( see table 1).35 ten unique 
 tlrs have been characterized in humans . of these , tlrs 1 , 2 , 4 , 5 , and 6 are expressed on the cell 
 membrane , while tlrs 3 , 7 , 8 , and 9 are expressed within the endolysosomal compartmental 
 pathway.3638 tlrs detect a number of different foreign molecules including : double 
 stranded deoxyribonucleic acid ( dna ) ( tlr3 ) , lipopolysaccharides ( tlr4 ) , flagellin ( tlr5 ) , 
 single - stranded viral ribonucleic acid ( rna ) ( tlr7/8 ) , and unmethylated cpg sites of dna of bacteria 
 and viruses ( tlr9).39 tlrs are expressed broadly 
 on hematopoietic cells , including dcs , plasma cells , monocytes , and b cells.30,35,40,41 tlr activation induces the expression of selectins , chemokines , and chemokine receptors , the 
 combination of which regulates migration of inflammatory cells).42,43 as reviewed by 
 smits et al,31 the administration of tlr7/8 
 agonists results in the secretion of multiple proinflammatory th1-type cytokines , including tumor 
 necrosis factor ( tnf)-alpha , interleukins 1 , 6 , and 8 , interferon - inducible protein 10 , monocyte 
 chemotactic protein 1 , interleukin 12p40 , interleukin-12p70 , and interleukin 18 . the molecular 
 pathways in tlr signaling have previously been reviewed . tlr7 is the therapeutic target of imiquimod , which has been used successfully in the treatment of 
 skin cancers.4446 given that tlr9 is expressed predominantly in b cells , it is 
 currently being explored in clinical trials for cutaneous lymphoma47 and leukemia.48 tlr8 is unique in the tlr family : the activation of tlr8 has a direct inhibitory effect on 
 tregs.49 the exact mechanism for this is unknown ; 
 however , tregs express tlr8,50 and the ability of 
 tlr8 to reverse treg inhibition is dendritic cell independent.31 tlr8 also likely has direct and indirect activating effects on 
 natural killer cells , causing them to produce interferon - gamma.40,51,52 the overall result of tlr8 activation is robust 
 enhancement of the innate immune response . additionally , tlr8 receptors have been demonstrated to 
 have variable expression within epithelial ovarian cancer tumors.53 the unique ability of tlr8 to reverse treg immunosuppression and augment immunity in the tumor 
 microenvironment makes it an ideal target for ovarian cancer therapy . vtx-2337 is a synthetic 
 small - molecule agonist that is specific to tlr8 , with a molecular weight of 458.6 daltons and a 
 molecular structure based on a 2-aminobenzazepine core . a recently published in vitro study40 using tlr - transfected human embryonic kidney cells 
 showed that vtx-2337 selectively activates tlr8 . the same study showed that vtx-2337 has the ability 
 to augment the immune response on multiple levels ( figure 
 1 ) : it induces mdcs and monocytes to produce high levels of interleukin-12 and tnf - alpha . it 
 directly stimulates natural killer cells to produce interferon - gamma and increases their lytic 
 activity . contrary to the traditionally immunosuppressive 
 effects of most systemic cytotoxic chemotherapy , doxorubicin has been reported to increase the tumor 
 cell surface exposure of calreticulin and the internalization of tumor cell antigens by phagocytic 
 dcs.54,55 furthermore , dying cancer cells have been shown to release high - mobility group box 1 
 protein , a ligand for tlr4 that has been reported to synergize with tlr8 to activate dcs and prime 
 t - cell response.40 therefore , vtx-2337 has the 
 potential to induce robust activation of the innate and adaptive immune response . a phase i clinical trial ( ntc00688415 ) , sponsored by ventirx pharmaceuticals ( seattle , wa , usa ) , 
 found vtx-2337 to be well tolerated and to have dose - dependent pharmacologic activity.56 as presented by cohen et al56 at the american society of clinical oncology ( asco ) 2011 meeting , the 
 inclusion criteria for this study were : ( 1 ) locally advanced or metastatic solid tumors or lymphoma , 
 and ( 2 ) eastern cooperative oncology group ( ecog ) performance status of 01 . the exclusion 
 criteria were : ( 1 ) anticancer therapy within 2 weeks , ( 2 ) immunosuppressive therapy within 2 weeks , 
 and ( 3 ) active autoimmune disease . in this study , vtx-2337 was administered to 33 patients with 
 advanced solid tumors ( the most common histologies were colorectal cancer , pancreatic cancer , and 
 melanoma ) , using a modified fibonacci dose escalation scheme . eight cohorts of 38 patients 
 received doses from 0.1 mg / m to 3.8 mg / m . there was an average of 3.1 years between the time of diagnosis and study entry . the most 
 common drug - related adverse events were grade 12 injection site reaction ( 85% ) , 
 chills ( 58% ) , fever ( 42% ) , and flu - like symptoms ( 24% ) . grade 3 hypotension 
 occurred in 1/6 patients and was the only dose - limiting toxicity . the primary outcome measures were 
 safety and the identification of dose - limiting toxicities and pharmacokinetics . the results showed 
 that the plasma levels of multiple immune mediators ( including granulocyte colony - stimulating factor 
 [ g - csf ] , monocyte chemotactic protein [ mcp]- 1 , macrophage 
 inflammatory protein [ mip]1-beta , and tnf - alpha ) were increased . as measured by the 
 response evaluation criteria in solid tumors ( recist ) criteria , 25% of patients demonstrated 
 disease stabilization at 8 weeks . gog-9925 ( study chair bj monk ) is a phase i trial undergone in collaboration with the national 
 cancer institute , nct01294293,57 evaluating the 
 side - effect profile and best dose of vtx-2337 and liposomal doxorubicin , in patients with persistent 
 or recurrent ovarian epithelial , fallopian tube , or peritoneal cancer . the primary outcomes are 
 first - cycle dose - limiting toxicity and the frequency / severity of toxicities . the secondary outcome 
 measures are immune activation and identification of the pharmacokinetics of vtx-2337 and pegylated 
 liposomal doxorubicin . enrollment criteria include measurable disease by recist 1.1 , or detectable 
 disease by ca-125 measurement , or other solid abnormalities on radiographic imaging . enrolled 
 patients have one prior platinum - based chemotherapeutic regimen and recurrence of disease within a 
 12-month platinum - free interval and do not have evidence of central nervous system ( cns ) metastasis . 
 this multicenter , dose - escalating study enrolled patients from april 2011 to june 2012.57 no results have yet been published from this 
 trial . a phase ii randomized , double - blind , placebo - controlled study is also now underway . known as gog 
 partners-3003 ( study chair bj monk ) , nct01666444 this trial is sponsored by ventirx pharmaceuticals 
 in collaboration with the gog partners and enrolls patients with recurrent or persistent 
 platinum - resistant epithelial ovarian , fallopian tube , or primary peritoneal carcinoma , with 
 measurable disease by recist 1.1 criteria and at least one target lesion . figure 2 shows a schema of the trial structure : the investigational arm 
 is vtx-2337 plus standard regimen pegylated liposomal doxorubicin ( pld ) . patients who have previously been treated with vtx-2337 , 
 doxorubicin , pld , or other anthracycline , patients receiving immunosuppressive therapy for any 
 reason , and patients with active autoimmune disease are excluded from this study . 3.0 
 mg / m of vtx-2337 or placebo will be administered as a subcutaneous injection on days 3 , 
 10 , and 17 of the first four 28-day treatment cycles and thereafter , on cycle day 3 only . the 
 primary outcome will be overall survival , with a planned analysis to occur approximately 15 months 
 after the last patient is enrolled . secondary outcomes will be the frequency and nature of 
 side - effects of vtx-2337 and progression - free survival using immune related response evaluation 
 criteria in solid tumors . exploratory objectives include the assessment of the effect of tlr8 polymorphisms and immune cell 
 subsets ( as measured by immunohistochemistry in primary tumor tissue ) on clinical outcomes , such as 
 overall survival , progression - free survival , and overall response rate.58 in conclusion , ovarian cancer remains a deadly disease , and new therapeutic approaches are 
 needed . the immunosuppressive microenvironment present in ovarian tumors represents a pathologic 
 process that is a prime target for novel therapies . indeed , the 2011 nobel prize in medicine or 
 physiology highlights that tlrs are the gateway to activating the innate immune response , and it 
 appears that tlr8 ligands are in a unique position to augment the current treatment of patients with 
 ovarian cancer . novel immunotherapeutic strategies and manipulation of the micro - enviroment may hold 
 the key to future success in ovarian cancer therapy .
ovarian cancer is the most deadly gynecologic cancer , with 15,000 anticipated deaths within the 
 united states alone in 2012 , and new treatment strategies are needed . 
 ovarian cancer tumors are 
 known to host an immunosuppressive microenvironment . 
 this suppression may be reversible via 
 activation of the innate immune response . 
 toll - like receptor 8 activates innate immunity while 
 simultaneously inhibiting the effects of regulatory t cells within the ovarian cancer tumors . 
 vtx-2337 is a novel small molecule ligand of toll - like receptor 8 and is currently the subject of a 
 phase ii randomized , double - blind , placebo - controlled trial gynecologic oncology group ( gog)-3003 
 for patients with recurrent platinum - resistant ovarian cancer . 
 we look forward to the results of 
 this trial as support for the paradigm of process therapy in the treatment of ovarian cancer .