Mirvetuximab Soravtansine in FRα-Positive, Platinum-Resistant Ovarian Cancer.

BACKGROUND: Mirvetuximab soravtansine-gynx (MIRV), a first-in-class antibody-drug conjugate targeting folate receptor α (FRα), is approved for the treatment of platinum-resistant ovarian cancer in the United States. METHODS: We conducted a phase 3, global, confirmatory, open-label, randomized, controlled trial to compare the efficacy and safety of MIRV with the investigator's choice of chemotherapy in the treatment of platinum-resistant, high-grade serous ovarian cancer. Participants who had previously received one to three lines of therapy and had high FRα tumor expression (≥75% of cells with ≥2+ staining intensity) were randomly assigned in a 1:1 ratio to receive MIRV (6 mg per kilogram of adjusted ideal body weight every 3 weeks) or chemotherapy (paclitaxel, pegylated liposomal doxorubicin, or topotecan). The primary end point was investigator-assessed progression-free survival; key secondary analytic end points included objective response, overall survival, and participant-reported outcomes. RESULTS: A total of 453 participants underwent randomization; 227 were assigned to the MIRV group and 226 to the chemotherapy group. The median progression-free survival was 5.62 months (95% confidence interval [CI], 4.34 to 5.95) with MIRV and 3.98 months (95% CI, 2.86 to 4.47) with chemotherapy (P<0.001). An objective response occurred in 42.3% of the participants in the MIRV group and in 15.9% of those in the chemotherapy group (odds ratio, 3.81; 95% CI, 2.44 to 5.94; P<0.001). Overall survival was significantly longer with MIRV than with chemotherapy (median, 16.46 months vs. 12.75 months; hazard ratio for death, 0.67; 95% CI, 0.50 to 0.89; P = 0.005). During the treatment period, fewer adverse events of grade 3 or higher occurred with MIRV than with chemotherapy (41.7% vs. 54.1%), as did serious adverse events of any grade (23.9% vs. 32.9%) and events leading to discontinuation (9.2% vs. 15.9%). CONCLUSIONS: Among participants with platinum-resistant, FRα-positive ovarian cancer, treatment with MIRV showed a significant benefit over chemotherapy with respect to progression-free and overall survival and objective response. (Funded by ImmunoGen; MIRASOL ClinicalTrials.gov number, NCT04209855.).

Chemical generation of small molecule-based bispecific antibody-drug conjugates for broadening the target scope.

Antibody-drug conjugates (ADCs) hold great therapeutic promise for cancer indications; however, treating tumors with intratumor heterogeneity remains challenging. We hypothesized that ADCs that can simultaneously target two different cancer antigens could address this issue. Here, we report controlled production and evaluation of bispecific ADCs chemically functionalized with tumor-targeting small molecules. Enzyme-mediated conjugation of bi-functional branched linkers and following sequential orthogonal click reactions with payload and tumor targeting modules (folic acid or RGD peptide) afforded homogeneous bispecific ADCs with defined ligand/drug-to-antibody ratios ranging from 4 + 4 to 16 + 4 (ligand/payload). Most bispecific ADCs were stable under physiological conditions for 14 days. Functionalization with the cancer-specific ligands did not impair cathepsin B-mediated payload release from ADCs. Bispecific ADCs targeting the folate receptor (FR)/human epidermal growth factor receptor 2 (HER2) demonstrated specific binding and high cell killing potency only in cells expressing either antigen (FR or HER2). Integrin/HER2 bispecific ADCs equipped with RGD peptides also showed target-specific binding and cytotoxicity in integrin- or HER2-positive cells. These findings suggest that our small-molecule based bispecific ADCs have the potential to effectively treat tumors with heterogeneous antigen expression.

Folate receptor-targeted RNAi nanoparticles for silencing STAT3 in tumor-associated macrophages and tumor cells.

We developed a STAT3 silencing siRNA to both tumor cells and M2 macrophages. The dual-targeting system prepared by electronic self-assembly was composed of folic acid-conjugated carboxymethyl chitosan for targeting and cationic chitosan derivatives for siRNA package. The effects of siRNA delivery was investigated in M2 macrophages and Lewis lung cancer cells (LLC). Due to the enhanced delivery efficiency, the dual-targeting delivery system exhibited a higher efficacy compared with non-targeting nanoparticles, resulting in a dramatically reduction of STAT3 expression in both cells, and a successful shift from M2 phenotypes (pro-tumor) to M1 phenotypes (anti-tumor) for macrophages. Additionally, the influence of the nanoparticles on LLC cells co-cultured with M2 macrophages was also investigated. The increased apoptosis and inhibition of proliferation of LLC cells were observed. In vivo therapeutic effect was also evaluated in s.c. tumor models, tumor growth was effectively inhibited and the level of M2 macrophages in tumor tissues was dramatically reduced.

Is Targeting the Folate Receptor in Ovarian Cancer Coming of Age?

Prognosis for women with epithelial ovarian cancer remains poor. One new molecular target in epithelial ovarian cancer is folate receptor alpha (FRα). This commentary discusses the characteristics that contribute to its attractiveness as a candidate for therapeutic intervention.

Antibody-drug conjugates in gynecologic malignancies.

Antibody drug conjugates (ADCs) are an exciting class of oncologic therapeutics. ADCs have been FDA approved in hematologic malignancies and breast cancer and are a growing area of study in numerous solid malignancies. The desire for tumor-specific therapies with decreased systemic toxicity has driven over a decade of research into the design and optimization of ADCs, which are now in a third generation of development. Gynecologic malignancies in particular suffer a dearth of novel therapies. This review will examine the field of ADCs in gynecologic cancers, focusing on ADCs targeting folate receptor alpha (FRα), mesothelin, tissue factor, MUC16 (CA125), NaPi2B, and Trop2.

Antibody-drug conjugates for ovarian cancer: current clinical development.

PURPOSE OF REVIEW: Antibody drug conjugates (ADC) are a novel class of cancer therapeutics, delivering cytotoxic therapy directly to cancer cells, and show promise in the management of platinum-resistant ovarian cancer. Herein we summarize the ADC landscape currently in clinical study. RECENT FINDINGS: Mirvetuximab Soravtansine, IMGN853, is an ADC targeting the folate receptor alpha (FRα) and has demonstrated promising single agent activity and a favorable toxicity profile in FRα-positive, platinum-resistant, epithelial ovarian cancer (EOC). The antitumor effect is seen primarily in less heavily pretreated EOC patients with moderate-to-high FRα tumor expression. A phase III study, randomizing patients to either IMGN853 or the physician's choice of single-agent chemotherapy has completed accrual. Additional ADC are being evaluated in ovarian cancer including agents that target NaPiB2, Trop2, mesothelin, and MUC16 are in phase 1 clinical trials. SUMMARY: ADC bind antigens overexpressed on cancer cells and provide site-selective drug delivery, with the goal to increase therapeutic efficacy of cytotoxics while decreasing the off-target toxicity of the payloads. With appropriate antigen selection and adequate, measurable antigen threshold targets, these new agents may provide an improved strategy for overcoming resistance to standard chemotherapy in ovarian cancer.

Prevention of behavioral deficits in rats exposed to folate receptor antibodies: implication in autism.

Folate receptor alpha (FRα) autoantibodies have been associated with fetal abnormalities and cerebral folate deficiency-related developmental disorders. Over 70% of the children with autism spectrum disorders (ASD) are positive for these autoantibodies and high-dose folinic acid is beneficial in treating these children. Here we show that antibodies (Abs) to the rat FRα administered during gestation produce communication, learning and cognitive deficits in a rat model that can be prevented by folinic acid and dexamethasone. FRα Ab can trigger inflammation as well as block folate transport to the fetus and to the developing brain to produce the functional deficits. In humans, exposure to FRα autoantibodies during fetal development and infancy could contribute to brain dysfunction such as that seen in ASD and other developmental disorders. Identifying women positive for the autoantibody and treating them with high-dose folinic acid along with other interventions to lower the autoantibody titer are effective strategies that may be considered to reduce the risk of having a child with developmental deficits.

Safety and activity findings from a phase 1b escalation study of mirvetuximab soravtansine, a folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC), in combination with carboplatin in patients with platinum-sensitive ovarian cancer.

PURPOSE: To evaluate the safety profile and preliminary antitumor activity of mirvetuximab soravtansine when administered in combination with carboplatin to relapsed ovarian cancer patients. METHODS: Patients with recurrent, platinum-sensitive epithelial ovarian or fallopian tube cancer were enrolled. Eligibility included a minimum requirement of tumor FRα positivity (≥25% of cells with ≥2+ staining intensity). Patients received escalating doses of mirvetuximab soravtansine and carboplatin on day 1 of a 21-day cycle (once every 3 weeks). Mirvetuximab soravtansine maintenance therapy was permitted, at the investigators discretion, following cessation of carboplatin treatment. Adverse events, tumor response, and progression-free survival (PFS) were determined. RESULTS: Eighteen patients were enrolled and dosed with combination therapy; thirteen continued with mirvetuximab soravtansine maintenance following carboplatin discontinuation. Mirvetuximab soravtansine dosing was escalated from 5 to 6 mg/kg (adjusted ideal body weight) and carboplatin from AUC4 to AUC5. Adverse events were generally mild (≤ grade 2) with nausea, diarrhea, thrombocytopenia, blurred vision, and fatigue being the most common treatment-emergent toxicities. For all evaluable patients (n = 17), the confirmed objective response rate (ORR) was 71%, including three complete responses and nine partial responses, and the median PFS was 15 months. A median duration of response was not reached. CONCLUSION: These data demonstrate that mirvetuximab soravtansine combined with carboplatin is a well-tolerated and highly active regimen in recurrent, platinum-sensitive ovarian cancer. Further evaluation of this combination in a randomized fashion is warranted.

A review of mirvetuximab soravtansine in the treatment of platinum-resistant ovarian cancer.

Resistance to platinum-based therapy poses a significant clinical challenge for the management of advanced ovarian cancer, a leading cause of cancer mortality among women. Mirvetuximab soravtansine is a novel antibody-drug conjugate that targets folate receptor-α, a validated molecular target for therapeutic intervention in this disease. Here, we examine mirvetuximab soravtansine's mechanism of action and pharmacology, and review its clinical evaluation in ovarian cancer to date. We focus on the favorable tolerability and encouraging signals of efficacy that have emerged, most notably in patients with platinum-resistant disease. Ongoing Phase III monotherapy and Phase Ib/II combination trials evaluating its activity in the setting of platinum resistance are emphasized, which will help define its role in the evolving landscape of ovarian cancer therapy.

Chemically Programmed Bispecific Antibodies in Diabody Format.

Chemically programmed bispecific antibodies (biAbs) endow target cell-binding small molecules with the ability to recruit and activate effector cells of the immune system. Here we report a platform of chemically programmed biAbs aimed at redirecting cytotoxic T cells to eliminate cancer cells. Two different antibody technologies were merged together to make a novel chemically programmed biAb. This was achieved by combining the humanized anti-hapten monoclonal antibody (mAb) h38C2 with the humanized anti-human CD3 mAb v9 in a clinically investigated diabody format known as Dual-Affinity Re-Targeting (DART). We show that h38C2 × v9 DARTs can readily be equipped with tumor-targeting hapten-derivatized small molecules without causing a systemic response harming healthy tissues. As a proof of concept, we chemically programmed h38C2 × v9 with hapten-folate and demonstrated its selectivity and potency against folate receptor 1 (FOLR1)-expressing ovarian cancer cells in vitro and in vivo Unlike conventional biAbs, chemically programmed biAbs in DART format are highly modular with broad utility in terms of both target and effector cell engagement. Most importantly, they provide tumor-targeting compounds access to the power of cancer immunotherapy.

Targeting of herbal bioactives through folate receptors: a novel concept to enhance intracellular drug delivery in cancer therapy.

Targeted drug delivery through folate receptor (FR) has emerged as a most biocompatible, target oriented, and non-immunogenic cargoes for the delivery of anticancer drugs. FRs are highly overexpressed in many tumor cells (like ovarian, lung, breast, kidney, brain, endometrial, and colon cancer), and targeting them through conjugates bearing specific ligand with encapsulated nanodrug moiety is undoubtedly, a promising approach toward tumor targeting. Folate, being an endogenous ligand, can be exploited well to affect various cellular events occurring during the progress of tumor, in a more natural and definite way. Thus, the aim of the review lies in summarizing the advancements taken place in the drug delivery system of different therapeutics through FRs and to refine its role as an endogenous ligand, in targeting of synthetic as well as natural bioactives. The review also provides an update on the patents received on the folate-based drug delivery system.

Folate Receptor Alpha Upregulates Oct4, Sox2 and Klf4 and Downregulates miR-138 and miR-let-7 in Cranial Neural Crest Cells.

Prenatal folic acid (FA) supplementation prevents neural tube defects. Folate receptor alpha (FRα) is critical for embryonic development, including neural crest (NC) development. Previously we showed that FRα translocates to the nucleus in response to FA, where it acts as a transcription factor. In this study, we examined if FA through interaction with FRα regulates stem cell characteristics of cranial neural crest cells (CNCCs)-critical for normal development. We hypothesized that FRα upregulates coding genes and simultaneously downregulates non-coding miRNA which targets coding genes in CNCCs. Quantitative RT-PCR and chromatin immunoprecipitation showed that FRα upregulates Oct4, Sox2, and Klf4 by binding to their cis-regulator elements-5' enhancer/promoters defined by H3K27Ac and p300 occupancy. FA via FRα downregulates miRNAs, miR-138 and miR-let-7, which target Oct4 and Trim71 (an Oct4 downstream effector), respectively. Co-immunoprecipitation data suggests that FRα interacts with the Drosha-DGCR8 complex to affect pre-miRNA processing. Transfecting anti-miR-138 or anti-miR-let-7 into non-proliferating neural crest cells (NCCs) derived from Splotch (Sp-/- ), restored their proliferation potential. In summary, these results suggest a novel pleiotropic role of FRα: (a) direct activation of Oct4, Sox2, and Klf4 genes; and (b) repression of biogenesis of miRNAs that target these genes or their effector molecules. Stem Cells 2016;34:2721-2732.

Improved Intraoperative Detection of Ovarian Cancer by Folate Receptor Alpha Targeted Dual-Modality Imaging.

Complete resection of tumor lesions in advanced stage ovarian cancer patients is of utmost importance, since the extent of residual disease after surgery strongly affects survival. Intraoperative imaging may be useful to improve surgery in these patients. Farletuzumab is a humanized IgG1 antibody that specifically recognizes the folate receptor alpha (FRα). Labeled with a radiolabel and a fluorescent dye, farletuzumab may be used for the intraoperative detection of ovarian cancer lesions. The current aim is to demonstrate the feasibility of FRα-targeted dual-modality imaging using 111In-farletuzumab-IRDye800CW in an intraperitoneal ovarian cancer model. Biodistribution studies were performed 3 days after injection of 3, 10, 30, or 100 µg of 111In-farletuzumab-IRDye800CW in mice with subcutaneous IGROV-1 tumors (5 mice per group). In mice with intraperitoneal IGROV-1 tumors the nonspecific uptake of 111In-farletuzumab-IRDye800CW was determined by coinjecting an excess of unlabeled farletuzumab. MicroSPECT/CT and fluorescence imaging were performed 3 days after injection of 10 µg of 111In-farletuzumab-IRDye800CW. FRα expression in tumors was determined immunohistochemically. Optimal tumor-to-blood-ratios (3.4-3.7) were obtained at protein doses up to 30 µg. Multiple intra-abdominal tumor lesions were clearly visualized by microSPECT/CT, while uptake in normal tissues was limited. Fluorescence imaging was used to visualize and guide resection of superficial tumors. Coinjection of an excess of unlabeled farletuzumab significantly decreased tumor uptake of 111In-farletuzumab-IRDye800CW (69.4 ± 27.6 versus 18.3 ± 2.2% ID/g, p < 0.05). Immunohistochemical analyses demonstrated that the radioactive and fluorescent signal corresponded with FRα-expressing tumor lesions. FRα-targeted SPECT/fluorescence imaging using 111In-farletuzumab-IRDye800CW can be used to detect ovarian cancer in vivo and could be a valuable tool for enhanced intraoperative tumor visualization in patients with intraperitoneal metastases of ovarian cancer.

Role of the folate receptor in ovarian cancer treatment: evidence, mechanism, and clinical implications.

Folate can be transported into the cell by the reduced folate carrier (RFC), the proton-coupled folate transporter (PCFT), or the folate receptor (FR), of which various isoforms exist. While the RFC and PCFT are expressed by many normal cells, the FR is present only in a small proportion of normal tissues. In these tissues, the FR expression level is often low and restricted to the apical surface of polarized epithelial cells. In contrast, FR is expressed on the blood-accessible basal and lateral membranes of many types of epithelial cancer. Considering that FR is expressed in few nonmalignant cell types on luminal membranes generally not accessible for molecules transported in the blood, FR is considered a promising antitumor target. As FR expression seems associated with tumor progression and prognosis, anticancer therapies targeting FR are currently being developed, such as farletuzumab (Morphotek, Exton, PA, USA), IMGN853 (ImmunoGen, Waltham, MA, USA), vintafolide, and EC1456 (both Endocyte Inc., West Lafayette, IN, USA). FR expression could be used as a response-predictive biomarker for these treatments. The ability to identify patients and treat them with an effective therapy based on the known expression of the tumor marker would, indeed, be the next step in predictive medicine for these patients. This review summarizes the role of FR in ovarian cancer and the value of FR as a prognostic biomarker for ovarian cancer and a response-predictive biomarker for folate-targeted therapeutics.

Levels of folate receptor autoantibodies in maternal and cord blood and risk of neural tube defects in a Chinese population.

BACKGROUND: After years of periconceptional folic acid supplementation, the prevalence of neural tube defects (NTDs) remains stable following the remarkable reduction observed immediately after the fortification practice. There is accumulating evidence that folate receptor (FR) autoimmunity may play a role in the etiology of folate-sensitive NTDs. METHODS: From 2011 to 2013, 118 NTD cases and 242 healthy controls were recruited from a population-based birth defects surveillance system in Northern China. Enzyme-linked immunosorbent assay was used to measure FR autoantibodies in maternal and cord blood. Logistic regression models were used to estimate the odds ratios (OR) and 95% confidence intervals (95% CI). RESULTS: Plasma FR autoantibodies levels were significantly elevated in mothers of infants with NTDs compared with mothers of healthy controls. Using the lowest tertile as the referent group, 2.20-fold (95% CI, 0.71-6.80) and 5.53-fold increased odds (95% CI, 1.90-16.08) of NTDs were observed for the second and third tertile of immunoglobulin G (IgG), respectively, and the odds of NTDs for each successive tertile of IgM was 0.98 (95% CI, 0.35-2.75) and 3.49 (95% CI, 1.45-8.39), respectively. A dose-response relationship was found between FR autoantibodies levels and risk of NTDs (P < 0.001 for IgG, P = 0.002 for IgM). The same pattern was observed in both subtypes of spina bifida and anencephaly. No significant difference in levels of cord blood FR autoantibodies was observed. CONCLUSION: Higher levels of FR autoimmunity in maternal plasma are associated with elevated risk of NTDs in a dose-response manner. Birth Defects Research (Part A) 106:685-695, 2016. © 2016 Wiley Periodicals, Inc.

Synthesis and Evaluation of (99m)Tc-Labeled Dimeric Folic Acid for FR-Targeting.

The folate receptor (FR) is overexpressed in a wide variety of human tumors. In our study, the multimeric concept was used to synthesize a dimeric folate derivative via a click reaction. The novel folate derivative (HYNIC-D1-FA2) was radiolabeled with (99m)Tc using tricine and trisodium triphenylphosphine-3,3',3″-trisulfonate (TPPTS) as coligands ((99m)Tc-HYNIC-D1-FA2) and its in vitro physicochemical properties, ex vivo biodistribution and in vivo micro-SPECT/CT imaging as a potential FR targeted agent were evaluated. It is a hydrophilic compound (log P = -2.52 ± 0.13) with high binding affinity (IC50 = 19.06 nM). Biodistribution in KB tumor-bearing mice showed that (99m)Tc-HYNIC-D1-FA2 had high uptake in FR overexpressed tumor and kidney at all time-points, and both of them could obviously be inhibited when blocking with free FA in the blocking studies. From the in vivo micro-SPECT/CT imaging results, good tumor uptake of (99m)Tc-HYNIC-D1-FA2 was observed in KB tumor-bearing mice and it could be blocked obviously. Based on the results, this new radiolabeled dimeric FA tracer might be a promising candidate for FR-targeting imaging with high affinity and selectivity.

Targeting the folate receptor: diagnostic and therapeutic approaches to personalize cancer treatments.

BACKGROUND: In cancer therapy, molecularly targeted agents have the potential to maximize antitumor efficacy while minimizing treatment-related toxicity. However, these agents may only be effective in specific tumor subtypes with defined genomic profiles. This emphasizes the importance of developing personalized cancer therapeutic strategies (i.e. through the use of companion diagnostic tests) to appropriately select and treat patients who are likely to benefit from specific targeted therapies, thus leading to improvements in clinical and safety outcomes. A potential biological target is the folate receptor (FR), which has been shown to be overexpressed on the surface of many cancers, including tumors of the lungs and ovaries. DESIGN: We carried out a literature search to identify how the FR can be a potential target for selected tumors, and how the FR expression can be exploited by targeted therapies. RESULTS: The two main therapeutic strategies for targeting the FR are based on the use of: (i) an anti-FR antibody (e.g. farletuzumab) and (ii) folate conjugates of folate-targeted chemotherapies and companion radiodiagnostic imaging agents (e.g. vintafolide and (99m)technetium-etarfolatide). Both of these strategies are being assessed in phase III trials. CONCLUSIONS: The important role that the FR plays in cancer development and progression has led to the development of FR-targeted therapeutic approaches. To date, the promising data observed in phase II clinical trials have not been confirmed in phase III studies. Accordingly, there is a need for further research in the refinement of patient selection and identification of new therapeutic combinations. In particular, the development of these targeted therapies requires reliable methods to be developed to detect FR-positive tumors in order to help select patients who may benefit from treatment.

Fischer 344 Rat: A Preclinical Model for Epithelial Ovarian Cancer Folate-Targeted Therapy.

OBJECTIVE: Ovarian cancer prognosis remains dire after primary therapy. Recurrence rates are disappointingly high as 60% of women with advanced epithelial ovarian cancer considered in remission will develop recurrent disease within 5 years. Special attention to undetected peritoneal metastasis and residual tumorous cells during surgery is necessary as they are the main predictive factors of recurrences. Folate receptor α (FRα) shows promising prospects in targeting ovarian cancerous cells. Our aim was to determine if the Fischer model described by Rose et al could be used to evaluate folate-targeted therapies in preclinical studies. METHODS: NuTu-19 epithelial ovarian cancer cell line was used to induce peritoneal carcinomatosis in female Fischer 344 rats. FRα expression by NuTu-19 cells was assessed in vitro by immunofluorescence using "Cytospin®" protocol. In vitro folate-targeted compound uptake by NuTu-19 cells was evaluated by incubation of FRα-positive ovarian cancer cell lines (NuTu-19/SKOV-3/OVCAR-3/IGROV-1) with or without (control) a folate-targeted photosensitizer. Intracellular incorporation was assessed by confocal microscopy. Determination of in vivo FRα tissue expression by several organs of the peritoneal cavity was studied by immunohistochemistry. RESULTS: NuTu-19 cells express FRα which allows intracellular incorporation of folate-targeted compound by endocytosis. FRα is expressed in tumor tissue, ovary, and liver. Peritoneum, colon, small intestine, and kidney do not express the receptor. CONCLUSIONS: Female Fischer 344 rat is an inexpensive reproducible and efficient preclinical model to study ovarian peritoneal carcinomatosis folate-targeted therapies.

Development of a folate receptor (FR)-targeted indenoisoquinoline using a pH-sensitive N-ethoxybenzylimidazole (NEBI) bifunctional cross-linker.

This Communication describes the synthesis and evaluation of a folate-conjugated drug delivery system (DDS) that incorporates an acid-sensitive N-ethoxybenzylimidazole (NEBI) bifunctional linker and a novel imidazole-containing indenoisoquinoline. Indenoisoquinolines are a class of TOP1 inhibitors that exhibit broad anticancer activity. Here, we examined whether a DDS that comprised an indenoisoquinoline attached to a folate moiety could help target activity to cancer cells that naturally overexpress the folate receptor (FR), thereby increasing the specificity of these compounds. Evaluation of the DDS revealed an 11-fold increased toxicity in folate receptor (FR)-overexpressing cells compared to in FR-knockdown cancer cells. Microscopy studies demonstrate enhanced internalization and localization of the DDS in acidic lysosomal compartments of FR-overexpressing cells, supporting a receptor-mediated mechanism for uptake and activation. Together with control experiments, the results support that the cytotoxic activity of this DDS is dependent on both the presence of the folate group as well as the presence of the acid-sensitive hydrolyzable group. This work represents the first example of a cell receptor-targeted indenoisoquinoline, which could help pave the way for the use of this class of compounds in anticancer therapy.

Folate and folate receptor alpha antagonists mechanism of action in ovarian cancer.

OBJECTIVE: The goal of this report is to review the activity of promising antifolate and folate receptor agents being developed for ovarian cancer including thymidylate synthase inhibitors, antifolate receptor antibodies, and folate-chemotherapy conjugates. METHODS: A literature search was performed over the last 5 years using the terms "folate receptor" and "ovarian cancer" and those that specifically addressed the MOA were included. Abstracts presented within the last 3 years were also searched and included in this review where appropriate. RESULTS: Thymidylate synthase inhibitors are a promising avenue for ovarian cancer treatment. Phase II trials have shown pemetrexed to have activity in patients with platinum resistant ovarian cancer. Several other thymidylate synthase inhibitors are in the early phase of development including BGC 945 and ZD-9331. Monoclonal antibodies that target the folate receptor have also shown potential in the development of ovarian cancer therapies. Farletuzumab is one of these antibodies. A recent phase III trial found that farletuzumab in combination with carboplatin and taxane did not meet the study's primary endpoint of progression-free survival (PFS). The post hoc exploratory analysis showed, however, a trend toward improved PFS in some patient subsets and further analysis is ongoing. The folate receptor is also utilized through folate conjugates. Vintafolide is one such agent which is currently in phase III development. Encouraging data from phase II trials showed an improvement in PFS from 2.7 months to 5 months. Folate can also be conjugated to radioisotopes for both therapeutic and imaging purposes, and early studies have shown correlation with amount of disease to therapy response. CONCLUSION: Folate targeted agents continue to show promising antitumor activity in ovarian malignancy and initial clinical experience has demonstrated favorable toxicity profiles. Further development and resources targeted toward these therapies appear to be warranted.