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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. 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. 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%). 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.).

Folate receptor-α (FRα) is overexpressed in many cancer cells and is therefore an important therapeutic target: here the X-ray crystal structure of folate-bound FRα is presented, revealing details of the ligand-binding pocket that may be useful in the development of small-molecule inhibitors for anticancer therapy. Folic acid receptor structure Folic acid, or folate, is an essential vitamin that is needed for many biological processes, including DNA synthesis, DNA repair and cell division. 'Normal' cells express relatively low amounts of the three folate receptors α, β and γ, but they are commonly overexpressed in cancer cell lines; for this reason, they are potential targets for new chemotherapeutics and cancer-imaging reagents. In this manuscript, the authors solve the X-ray crystal structure of the folate-bound form of human folate receptor α, which mediates folate uptake into cells. The authors map the ligand-binding pocket, providing data that should be useful for the development of new small molecules to target the receptor. Folate receptors (FRα, FRβ and FRγ) are cysteine-rich cell-surface glycoproteins that bind folate with high affinity to mediate cellular uptake of folate. Although expressed at very low levels in most tissues, folate receptors, especially FRα, are expressed at high levels in numerous cancers to meet the folate demand of rapidly dividing cells under low folate conditions 1 , 2 , 3 . The folate dependency of many tumours has been therapeutically and diagnostically exploited by administration of anti-FRα antibodies, high-affinity antifolates 4 , 5 , folate-based imaging agents and folate-conjugated drugs and toxins 6 , 7 , 8 . To understand how folate binds its receptors, we determined the crystal structure of human FRα in complex with folic acid at 2.8 Å resolution. FRα has a globular structure stabilized by eight disulphide bonds and contains a deep open folate-binding pocket comprised of residues that are conserved in all receptor subtypes. The folate pteroate moiety is buried inside the receptor, whereas its glutamate moiety is solvent-exposed and sticks out of the pocket entrance, allowing it to be conjugated to drugs without adversely affecting FRα binding. The extensive interactions between the receptor and ligand readily explain the high folate-binding affinity of folate receptors and provide a template for designing more specific drugs targeting the folate receptor system.

Cerebral folate deficiency syndrome (CFDS) is defined as any neuropsychiatric or developmental disorder characterized by decreased CSF folate levels in the presence of normal folate status outside the nervous system. The specific clinical profile appears to be largely determined by the presence or absence of intrauterine folate deficiency as well as postnatal age at which cerebral folate deficiency occurs. The primary cause of CFDS is identified as the presence of serum folate receptor-alpha (FRα) autoantibodies impairing folate transport across the choroid plexus to the brain whereas, in a minority of cases, mitochondrial disorders, inborn errors of metabolism and loss of function mutations of the FRα (FOLR1) gene are identified. Early recognition and diagnosis of CFDS and prompt intervention is important to improve prognosis with successful outcomes. In this article we focus on FRα autoimmunity and its different age-dependent clinical syndromes, the diagnostic criteria, and treatments to be considered, including prevention strategies in this at-risk population.

Mirvetuximab soravtansine-gynx (MIRV) is a first-in-class antibody–drug conjugate targeting folate receptor α (FRα), approved by the US Food and Drug Administration for the treatment of platinum-resistant ovarian cancer in the USA. Here, we report patient-reported outcomes for participants treated with MIRV compared with investigator's choice of chemotherapy from the phase 3 MIRASOL trial, which met its primary endpoint of progression-free survival and key secondary endpoints of objective response rate and overall survival. The MIRASOL trial was a confirmatory, phase 3, randomised, controlled, open-label trial, building on the phase 2 SORAYA trial which had previously demonstrated the safety and efficacy of MIRV in platinum-resistant ovarian cancer. Patients 18 years or older with a confirmed platinum-resistant, recurrent high-grade serous epithelial ovarian cancer diagnosis were recruited from 253 sites including hospitals, academic centres, and community centres in 21 countries. Patients must have received one to three previous systemic anticancer therapies, and have high FRα tumour expression (≥75% tumour cells with an immunohistochemistry score of ≥2+ membrane staining using the PS2+ scoring method), one or more lesions with measurable disease, and an Eastern Cooperative Oncology Group performance status of 0 or 1. Patients were randomly assigned (1:1) to MIRV or investigator's choice of chemotherapy, stratified by number of previous therapy lines and the type of investigator's choice of chemotherapy. Therapies were administered in an open-label manner; MIRV was administered intravenously at 6 mg/kg of adjusted ideal bodyweight every 3 weeks. The primary endpoint was progression-free survival. Key secondary endpoints were objective response rate, overall survival, and a 15·0-point or greater improvement at week 8 or 9 in abdominal and gastrointestinal symptoms using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Ovarian Cancer Module (EORTC QLQ-OV28) in the intention-to-treat population. The MIRASOL trial was registered at ClinicalTrials.gov (NCT04209855), the Gynecologic Oncology Group (GOG 3045), and the European Network of Gynaecological Oncological Trial Groups (ENGOT-ov55), and is complete. Between Feb 3, 2020, and Aug 3, 2022, 453 patients were enrolled and randomly assigned to treatment (227 to the MIRV group and 226 to the investigator's choice of chemotherapy group). All patients were female; 301 (66%) participants were White, 53 (12%) were Asian, 13 (3%) were Black, and 86 (19%) were of another race or not reported; 27 (6%) were Hispanic or Latino. The median follow-up for the study, determined by the reverse Kaplan–Meier method, was 13·1 months (95% CI 12·1–14). QLQ-OV28 completion rates were 86% (365 of 425) at baseline and 81% (282 of 349) at week 8 or 9. 34 (21·0%; 95% CI 15·0–28·1) of 162 patients treated with MIRV reported improvement in QLQ-OV28 abdominal and gastrointestinal scores, compared with 23 (15·3%; 10·0–22·1) of 150 patients treated with the investigator's choice of chemotherapy. These differences were not statistically significant (odds ratio 1·5 [95% CI 0·8–2·6]; p=0·26). MIRV did not seem to impair or improve patient quality of life compared with investigator's choice of chemotherapy. The similar quality-of-life outcomes in the two treatment groups, combined with the previously reported higher efficacy of MIRV compared with single-agent chemotherapy, support MIRV as new treatment option for FRα-positive platinum-resistant ovarian cancer. AbbVie.

We sought to determine whether high-dose folinic acid improves verbal communication in children with non-syndromic autism spectrum disorder (ASD) and language impairment in a double-blind placebo control setting. Forty-eight children (mean age 7 years 4 months; 82% male) with ASD and language impairment were randomized to receive 12 weeks of high-dose folinic acid (2 mg kg-1 per day, maximum 50 mg per day; n=23) or placebo (n=25). Children were subtyped by glutathione and folate receptor-α autoantibody (FRAA) status. Improvement in verbal communication, as measured by a ability-appropriate standardized instrument, was significantly greater in participants receiving folinic acid as compared with those receiving placebo, resulting in an effect of 5.7 (1.0,10.4) standardized points with a medium-to-large effect size (Cohen's d=0.70). FRAA status was predictive of response to treatment. For FRAA-positive participants, improvement in verbal communication was significantly greater in those receiving folinic acid as compared with those receiving placebo, resulting in an effect of 7.3 (1.4,13.2) standardized points with a large effect size (Cohen's d=0.91), indicating that folinic acid treatment may be more efficacious in children with ASD who are FRAA positive. Improvements in subscales of the Vineland Adaptive Behavior Scale, the Aberrant Behavior Checklist, the Autism Symptom Questionnaire and the Behavioral Assessment System for Children were significantly greater in the folinic acid group as compared with the placebo group. There was no significant difference in adverse effects between treatment groups. Thus, in this small trial of children with non-syndromic ASD and language impairment, treatment with high-dose folinic acid for 12 weeks resulted in improvement in verbal communication as compared with placebo, particularly in those participants who were positive for FRAAs.

Prostate cancer (PCa) remains a common cancer with high mortality in men due to its heterogeneity and the emergence of drug resistance. A critical factor contributing to its lethality is the presence of prostate cancer stem cells (PCSCs), which can self-renew, long-term propagate tumors, and mediate treatment resistance. MicroRNA-34a (miR-34a) has shown promise as an anti-PCSC therapeutic by targeting critical molecules involved in cancer stem cell (CSC) survival and functions. Despite extensive efforts, the development of miR-34a therapeutics still faces challenges, including non-specific delivery and delivery-associated toxicity. One emerging delivery approach is ligand-mediated conjugation, aiming to achieve specific delivery of miR-34a to cancer cells, thereby enhancing efficacy while minimizing toxicity. Folate-conjugated miR-34a (folate–miR-34a) has demonstrated promising anti-tumor efficacy in breast and lung cancers by targeting folate receptor α (FOLR1). Here, we first show that miR-34a, a TP53 transcriptional target, is reduced in PCa that harbors TP53 loss or mutations and that miR-34a mimic, when transfected into PCa cells, downregulated multiple miR-34a targets and inhibited cell growth. When exploring the therapeutic potential of folate–miR-34a, we found that folate–miR-34a exhibited impressive inhibitory effects on breast, ovarian, and cervical cancer cells but showed minimal effects on and targeted delivery to PCa cells due to a lack of appreciable expression of FOLR1 in PCa cells. Folate–miR-34a also did not display any apparent effect on PCa cells expressing prostate-specific membrane antigen (PMSA) despite the reported folate’s binding capability to PSMA. These results highlight challenges in the specific delivery of folate–miR-34a to PCa due to a lack of target (receptor) expression. Our study offers novel insights into the challenges and promises within the field and casts light on the development of ligand-conjugated miR-34a therapeutics for PCa.

Cerebral folate deficiency (CFD) syndrome is a neurodevelopmental disorder typically caused by folate receptor autoantibodies (FRAs) that interfere with folate transport across the blood–brain barrier. Autism spectrum disorders (ASDs) and improvements in ASD symptoms with leucovorin (folinic acid) treatment have been reported in some children with CFD. In children with ASD, the prevalence of FRAs and the response to leucovorin in FRA-positive children has not been systematically investigated. In this study, serum FRA concentrations were measured in 93 children with ASD and a high prevalence (75.3%) of FRAs was found. In 16 children, the concentration of blocking FRA significantly correlated with cerebrospinal fluid 5-methyltetrahydrofolate concentrations, which were below the normative mean in every case. Children with FRAs were treated with oral leucovorin calcium (2 mg kg −1 per day; maximum 50 mg per day). Treatment response was measured and compared with a wait-list control group. Compared with controls, significantly higher improvement ratings were observed in treated children over a mean period of 4 months in verbal communication, receptive and expressive language, attention and stereotypical behavior. Approximately one-third of treated children demonstrated moderate to much improvement. The incidence of adverse effects was low. This study suggests that FRAs may be important in ASD and that FRA-positive children with ASD may benefit from leucovorin calcium treatment. Given these results, empirical treatment with leucovorin calcium may be a reasonable and non-invasive approach in FRA-positive children with ASD. Additional studies of folate receptor autoimmunity and leucovorin calcium treatment in children with ASD are warranted.

The VENTANA FOLR1 (FOLR1-2.1) RxDx (FOLR1 CDx) assay, developed by Roche Tissue Diagnostics, is a Food and Drug Administration-approved immunohistochemical assay intended for use in the assessment of folate receptor α (FRα) expression in formalin-fixed, paraffin-embedded epithelial ovarian, fallopian tube, and primary peritoneal tumor specimens. No published reports have compared the performance of other available FRα antibodies with the approved FOLR1 CDx. To assess the performance of research FRα laboratory-developed tests compared with the FOLR1 CDx. The performance of 6 FRα-targeting antibodies was compared with the approved FOLR1 CDx in normal fallopian tube specimens. Two antibodies were selected for further assessment and compared with the FOLR1 CDx in ovarian tumor specimens. Of the 6 antibodies tested, 4 displayed a lack of specific membrane staining and/or high background, whereas 2 antibodies, produced by Leica Biosystems and Biocare Medical, respectively, exhibited specific and sensitive FRα staining. When assessed for their ability to correctly identify FRα-positive samples (per the FOLR1 CDx label, ≥75% of viable tumor cells with moderate and/or strong membranous staining intensity), both assays overpredicted FRα positivity compared with the FOLR1 CDx in archival ovarian tumor samples. These data highlight the need for caution in antibody selection when developing immunohistochemistry-based assays, as some antibodies failed to cleanly and specifically identify FRα expression. We identified 2 antibodies appropriate for further investigation; however, as developed, these antibodies may overselect patients for treatment with FRα-targeted therapies.

ObjectiveThe single-arm, phase II SORAYA trial (NCT04296890) of mirvetuximab soravtansine-gynx in folate receptor alpha (FRα)–high platinum-resistant ovarian cancer (n=105 (efficacy-evaluable)) met its primary endpoint with an objective response rate of 32.4% (95% CI, 23.6 to 42.2). Here we report final SORAYA trial results for overall survival and post hoc objective response rates in subgroups by sequence and number of prior therapies.MethodsEligible patients had high-grade serous platinum-resistant ovarian cancer with high FRα expression and one to three prior therapies (prior bevacizumab required). Enrolled participants received 6 mg/kg mirvetuximab soravtansine-gynx adjusted ideal body weight intravenously once every 3 weeks until progressive disease, unacceptable toxicity, withdrawal of consent, or death. Final overall survival and post hoc objective response rates were assessed in efficacy-evaluable participants. The safety population included all patients who received ≥1 dose of mirvetuximab soravtansine-gynx.ResultsAt data cut-off (December 22, 2022; n=105), final median overall survival was 15.0 months (95% CI, 11.5 to 18.7). Median overall survival in participants with one to two prior therapy lines was 18.7 months (95% CI, 13.8 to not estimable (NE)) and 11.6 months (95% CI, 7.1 to 16.7) with three prior therapy lines. Median overall survival was 15.0 months (95% CI, 11.5 to NE) in participants with prior poly (ADP-ribose) polymerase inhibitor (PARPi) treatment versus 14.0 months (95% CI, 7.1 to NE) in those without. Objective response rate (data cut-off: November 17, 2021) differed among participants who received mirvetuximab soravtansine-gynx as their first treatment in the platinum-resistant setting (34.8%; 95% CI, 23.5 to 47.6) versus a different first treatment (28.2%; 95% CI, 15.0 to 44.9) or had received prior bevacizumab in a platinum-sensitive (34.0%; 95% CI, 24.6 to 44.5) versus platinum-resistant setting (17.6%; 95% CI, 3.8 to 43.4). No new safety signals were observed.ConclusionThese results support the clinically meaningful efficacy of mirvetuximab soravtansine-gynx in FRα-expressing platinum-resistant ovarian cancer, irrespective of prior treatment or sequence.

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.