Prakash Ambady

What Does the Boxed Warning Tell Us? Safe Practice of Using Ferumoxytol as an MRI Contrast Agent

BACKGROUND AND PURPOSE: Despite the label change and the FDAs boxed warning added to the Feraheme (ferumoxytol) label in March 2015, radiologists have shown increasing interest in using ferumoxytol as an MR imaging contrast agent as a supplement or alternative to gadolinium. The goals of this study were to provide information regarding ferumoxytol safety as an imaging agent in a single center and to assess how the Feraheme label change may affect this potential, currently off-label indication. MATERIALS AND METHODS: This retrospective study evaluated the overall frequency of ferumoxytol-related adverse events when used for CNS MR imaging. Patients with various CNS pathologies were enrolled in institutional review board–approved imaging studies. Ferumoxytol was administered as multiple rapid bolus injections. The risk of adverse events was correlated with demographic data/medical history. RESULTS: The safety of 671 ferumoxytol-enhanced MR studies in 331 patients was analyzed. No anaphylactic, life-threatening, or fatal (grade 4 or 5) adverse events were recorded. The overall proportion of ferumoxytol-related grade 1–3 adverse events was 10.6% (8.6% occurring within 48 hours), including hypertension (2.38%), nausea (1.64%), diarrhea (1.04%), and headache (1.04%). History of 1 or 2 allergies was associated with an increased risk of adverse events (14.61% versus 7.51% [no history]; P = .007). CONCLUSIONS: The frequency of mild ferumoxytol-related adverse events was comparable with literature results, and no serious adverse event was recorded. Although the recommendations in the boxed warning should be followed, serious adverse events appear to be rare, and with proper precautions, ferumoxytol may be a valuable MR imaging agent.

Quantitative comparison of delayed ferumoxytol T1 enhancement with immediate gadoteridol enhancement in high grade gliomas

Delayed ferumoxytol enhancement on T1‐weighted images appears visually similar to gadoteridol enhancement. The purpose of this study was to quantitatively compare ferumoxytol T1 enhancement to gadoteridol enhancement with an objective, semi‐automated method.

Combination immunotherapy as a non-chemotherapy alternative for refractory or recurrent CNS lymphoma

Primary central nervous system lymphoma (PCNSL) is an extemely rare, CD20þ non-germinal center B cell lymphoma (diffuse large cell type) in a bed of T-cell rich tumor microenvironment. The prognostic or predictive significance of the T-cell infiltration in the tumor microenvironment is unclear, but provides an attractive therapeutic opportunity. Traditionally, high dose methotrexate (HD-MTX)-based regimens are considered as the standard of care in first-line therapy. Most centers include rituximab, an anti-CD20 antibody, in their regimens based on multiple retrospective studies and a randomized phase II trial [1]. The role of rituximab was recently challenged by the preliminary results of a prospective phase III trial that indicates no improvement in progression-free survival with the addition of rituximab for PCNSL. Rituximab is expected to continue to be a part of many first-line regimens until long-term follow up data including overall survival is available [2]. Although excellent responses have been reported with HD-MTX-based regimens, most patients relapse within the first two years [3–5]. In the absence of large randomized phase III trials, the optimum therapy for cases that are refractory or have relapsed after HD-MTX is not well defined; patients are generally re-challenged with HD-MTX-based regimens and receive whole brain radiotherapy (WBRT) or their combination, followed by myeloablative therapy and stem cell transplant. However, these therapies are associated with a high incidence of treatment-related toxicities and prognosis continues to be poor [6–8]. HD-MTX-based regimens require hospitalization for up to a week and are quite challenging for many patients, especially those with poor performance status, impaired renal function, or the inability to tolerate the aggressive hydration and alkalization necessary to safely administer HD-MTX. Similarly, WBRT is associated with significant neurocognitive dysfunction [9]. Safer and more effective alternatives are essential to improve outcomes and quality of life in this aggressive brain tumor. PD-L1 overexpression has been described in nongerminal center B-cell-like type of diffuse large B-cell lymphoma (DLBCL), suggesting that anti-PD-1/PD-L1 approaches may be beneficial in these types of tumors [10]. Since CNS lymphoma is a type of non-germinal center non-Hodgkin lymphoma and is also known to overexpress PD-L1 and -L2 receptors, there is significant interest in evaluating this approach in this aggressive tumor type [11]. Very limited low level evidence in the form of small retrospective studies demonstrate promising efficacy in recurrent/refractory CNS lymphoma with the off-label use of a PD-1 inhibitor as monotherapy [12]. Combining a check point inhibitor with an anti-CD20 antibody allows the simultaneous targeting of both CD20 malignant cells as well as T cells in the tumor microenvironment. Blocking PD-1 could enhance the antitumor activity of T cells that could be further enhanced by inducing antibody-dependent cellular cytotoxicity using an anti-CD20 antibody. Thus, this combination may result in the activation of both the innate and adaptive immune systems and in enhanced clinical response [13]. The combination of pembrolizumab and rituximab has been shown to be well tolerated with no additional autoimmune or treatment-related serious adverse events [14]. Between December 2015 and December 2017, six patients with relapsed or progressive CNS lymphoma were treated at our institution with the combination of off-label PD-1 inhibitor (five patients received pembrolizumab while one received nivolumab) and rituximab, an anti-CD20 monoclonal antibody. Their medical records were reviewed retrospectively after institutional review board approval. Images were reviewed and the response was assessed by a neuroradiologist. Three had systemic lymphoma with isolated CNS recurrences, the other three

Combined Iron Oxide Nanoparticle Ferumoxytol and Gadolinium Contrast Enhanced MRI Defines Glioblastoma Pseudo-progression

BACKGROUND Noninvasively differentiating therapy-induced pseudoprogression from recurrent disease in patients with glioblastoma is prospectively difficult due to the current lack of a biologically specific imaging metric. Ferumoxytol iron oxide nanoparticle MRI contrast characterizes innate immunity mediated neuroinflammation; therefore, we hypothesized that combined ferumoxytol and gadolinium enhanced MRI could serve as a biomarker of glioblastoma pseudoprogression. METHODS In this institutional review board-approved, retrospective study, we analyzed ferumoxytol and gadolinium contrast enhanced T1-weighted 3T MRI in 45 patients with glioblastoma over multiple clinical timepoints. Isocitrate dehydrogenase 1 (IDH-1) mutational status was characterized by exome sequencing. Sum of products diameter measurements were calculated according to Response Assessment in Neuro-Oncology criteria from both gadolinium and ferumoxytol enhanced sequences. Enhancement mismatch was calculated as the natural log of the ferumoxytol to gadolinium sum of products diameter ratio. Analysis of variance and Students t-test assessed differences in mismatch ratios. P-value <0.05 indicated statistical significance. RESULTS With the development of pseudoprogression we observed a significantly elevated mismatch ratio compared with disease recurrence (P < 0.01) within IDH-1 wild type patients. Patients with IDH-1 mutation demonstrated significantly reduced mismatch ratio with the development of pseudoprogression compared with disease recurrence (P < 0.01). Receiver operator curve analysis demonstrated 100% sensitivity and specificity for the use of mismatch ratios as a diagnostic biomarker of pseudoprogression. CONCLUSION Our study suggests that ferumoxytol to gadolinium contrast mismatch ratios are an MRI biomarker for the diagnosis of pseudoprogression in patients with glioblastoma. This may be due to the unique characterization of therapy-induced neuroinflammation.

Abstract B38: Radiation enhances intracellular delivery of anti-MGMT oligomers to reduce protein expression in vitro and in a xenograft model

High levels of DNA repair enzyme O6-methylguanine DNA methyltransferase (MGMT) in glioblastoma tumor are associated with temozolomide resistance and poor prognosis. MGMT provides a promising therapeutic target to overcome chemo-resistance and improve overall survival in cancer patients. In this study, we investigate the enhanced delivery of anti-MGMT morpholino oligonucleotide (AMON) using a sub-therapeutic dose of radiation to reduce MGMT expression of human cancer cells (T98G glioma and H460 and A549 non-small cell lung carcinoma) in vitro and in vivo. Compared to standard transfection techniques, sub-therapeutic dose of radiation enhanced intracellular AMON delivery and transiently reduced MGMT protein expression at 3 d in vitro. The optimal radiation dosage was cancer cell type dependent and ranged from 1-12 Gy. In addition, AMON delivered using sub-therapeutic dose of radiation increased cytotoxicity of T98G cells in response to temozolomide compared to radiation and temozolomide alone in vitro. In a H460 subcutaneous xenograft tumor model, intravenous AMON administration reduced MGMT protein level by 50% in irradiated tumors but not in contralateral non-irradiated lesions within the same animal. Tumor MGMT protein downregulation by AMON did not alter DNA promoter methylation status. Our results demonstrate for the first time the use of radiation to enhance the intracellular delivery of antisense oligonucleotides to modulate MGMT protein expression in vitro and in vivo. We have previously shown that antisense nucleotides can be delivered to the brain parenchyma using osmotic blood brain barrier disruption. Therefore, we believe that cancer patients with MGMT overexpression, unmethylated DNA promoter and/or resistance to DNA alkylating agents may benefit from this novel antisense therapeutic technology to improve overall survival. Citation Format: Jeffrey Wu, Prakash Ambady, DreeAnna Morris, Michael Pagel, Randy Woltjer, Joshua Walker, Leslie Muldoon, Edward Neuwelt. Radiation enhances intracellular delivery of anti-MGMT oligomers to reduce protein expression in vitro and in a xenograft model [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr B38.

Enhancing the cytotoxicity of chemoradiation with radiation-guided delivery of anti-MGMT morpholino oligonucleotides in non-methylated solid tumors

The DNA repair enzyme O6-methylguanine DNA methyltransferase (MGMT) is epigenetically silenced in some tumors by MGMT gene promoter methylation. MGMT-hypermethylated solid tumors have enhanced susceptibility to the cytotoxic effects of alkylating chemotherapy such as temozolomide, compared with non-methylated tumors. In glioblastoma, subjects with MGMT hypermethylation have significantly longer survival rates after chemoradiotherapy. We report the first successful use of a non-ablative dose of ionizing radiation to prime human cancer cells to enhance the uptake of unmodified anti-MGMT morpholino oligonucleotide (AMON) sequences. We demonstrate >40% reduction in the in vitro proliferation index and cell viability in radiation-primed MGMT-expressing human solid tumor cells treated with a single dose of AMONs and temozolomide. We further demonstrate the feasibility of using a non-ablative dose of radiation in vivo to guide and enhance the delivery of intravenously administered AMONs to achieve 50% MGMT knockdown only at radiation-primed tumor sites in a subcutaneous tumor model. Local upregulation of physiological endocytosis after radiation may have a role in radiation-guided uptake of AMONs. This approach holds direct translational significance in glioblastoma and brain metastases where radiation is part of the standard of care; our approach to silence MGMT could overcome the significant problem of MGMT-mediated chemoresistance.