The PET-Tracer 89Zr-Df-IAB22M2C Enables Monitoring of Intratumoral CD8 T-cell Infiltrates in Tumor-Bearing Humanized Mice after T-cell Bispecific Antibody Treatment.

CD8-expressing T cells are the main effector cells in cancer immunotherapy. Treatment-induced changes in intratumoral CD8+ T cells may represent a biomarker to identify patients responding to cancer immunotherapy. Here, we have used a 89Zr-radiolabeled human CD8-specific minibody (89Zr-Df-IAB22M2C) to monitor CD8+ T-cell tumor infiltrates by PET. The ability of this tracer to quantify CD8+ T-cell tumor infiltrates was evaluated in preclinical studies following single-agent treatment with FOLR1-T-cell bispecific (TCB) antibody and combination therapy of CEA-TCB (RG7802) and CEA-targeted 4-1BB agonist CEA-4-1BBL. In vitro cytotoxicity assays with peripheral blood mononuclear cells and CEA-expressing MKN-45 gastric or FOLR1-expressing HeLa cervical cancer cells confirmed noninterference of the anti-CD8-PET-tracer with the mode of action of CEA-TCB/CEA-4-1BBL and FOLR1-TCB at relevant doses. In vivo, the extent of tumor regression induced by combination treatment with CEA-TCB/CEA-4-1BBL in MKN-45 tumor-bearing humanized mice correlated with intratumoral CD8+ T-cell infiltration. This was detectable by 89Zr-IAB22M2C-PET and γ-counting. Similarly, single-agent treatment with FOLR1-TCB induced strong CD8+ T-cell infiltration in HeLa tumors, where 89Zr-Df-IAB22M2C again was able to detect CD8 tumor infiltrates. CD8-IHC confirmed the PET imaging results. Taken together, the anti-CD8-minibody 89Zr-Df-IAB22M2C revealed a high sensitivity for the detection of intratumoral CD8+ T-cell infiltrates upon either single or combination treatment with TCB antibody-based fusion proteins. These results provide further evidence that the anti-CD8 tracer, which is currently in clinical phase II, is a promising monitoring tool for intratumoral CD8+ T cells in patients treated with cancer immunotherapy. SIGNIFICANCE: Monitoring the pharmacodynamic activity of cancer immunotherapy with novel molecular imaging tools such as 89Zr-Df-IAB22M2C for PET imaging is of prime importance to identify patients responding early to cancer immunotherapy.

89Zr-labeled CEA-targeted IL-2 variant immunocytokine in patients with solid tumors: CEA-mediated tumor accumulation and role of IL-2 receptor-binding.

Cergutuzumab amunaleukin (CEA-IL2v) is an immunocytokine directed against carcinoembryonic antigen (CEA) containing an IL2v-moiety with abolished IL-2 receptor (IL-2R) α binding. We describe the biodistribution and tumor accumulation of 89Zr-labeled CEA-IL2v. Twenty-four patients with advanced solid CEA positive (CEA+) or negative (CEA-) tumors received CEA-IL2v 6 mg (4 CEA+; 3 CEA-), 20 mg (9 CEA+), or 30 mg (4 CEA+; 4 CEA-) biweekly. In cycle 1, 2 mg of the total dose comprised 89Zr-CEA-IL2v (50 MBq) and serial 89Zr-PET imaging was conducted. Four CEA+ patients with visually confirmed 89Zr-CEA-IL2v tumor accumulation at 20 mg had repeated 89Zr-PET imaging during cycle 4. 89Zr-CEA-IL2v immuno-PET demonstrated preferential drug accumulation in CEA+ tumors (%ID/mLpeak CEA- 3.6 × 10-3 vs. CEA+ 6.7 ×∙10-3). There was a non-significant trend towards dose-dependent tumor uptake, with higher uptake at doses ≥20 mg. Biodistribution was dose- and CEA-independent with major accumulation in lymphoid tissue compatible with IL-2R binding. Reduced exposure and reduced tumor accumulation (%ID/mLpeak 57% lower) on cycle 4 vs. cycle 1 was consistent with peripheral expansion of immune cells. The findings of this immune PET imaging study with 89Zr-CEA-IL2v support the therapeutic concept of CEA-IL2v, confirming selective and targeted tumor accumulation with this novel immunocytokine.

Dynamic contrast-enhanced MRI of vascular changes induced by the VEGF-signalling inhibitor ZD4190 in human tumour xenografts.

Dynamic contrast-enhanced magnetic resonance imaging (DCEMRI) was used to examine the acute effects of treatment with an inhibitor of vascular endothelial growth factor (VEGF) signaling. ZD4190 is an orally bioavailable inhibitor of VEGF receptor-2 (KDR) tyrosine kinase activity, which elicits broad-spectrum antitumour activity in preclinical models following chronic once-daily dosing. Nude mice, bearing established (0.5-1.0 mL volume) human prostate (PC-3), lung (Calu-6) and breast (MDA-MB-231) tumor xenografts, were dosed with ZD4190 (p.o.) using a 1 day (0 and 22 h) or 7 day (0, 24, 48, 72, 96,120,144, and 166 h) treatment regimen. DCEMRI was employed 2 h after the last dose of ZD4190, using the contrast agent gadopentetate dimeglumine. Dynamic data were fit to a compartmental model to obtain voxelwise K(trans), the transfer constant for gadopentetate into the tumor. K(trans) was averaged over the entire tumor, and a multi-threshold histogram analysis was also employed to account for tumor heterogeneity. Reductions in K(trans) reflect reductions in flow, in endothelial surface area, and/or in vascular permeability. A vascular input function was obtained for each mouse simultaneously with the tumor DCEMRI data. ZD4190 treatment produced a dose-dependent (12.5-100 mg x kg(-1) per dose) reduction in K(trans) in PC-3 prostate tumors. At 100 mg x kg(-1), the largest concentration examined, ZD4190 reduced K(trans) in PC-3 tumors by 31% following 2 doses (1 day treatment regimen; p < 0.001) and by 53% following 8 doses (7 day regimen; p < 0.001). Comparative studies in the three models using a showed similar reductions in K(trans) for the lung and breast tumors using the histogram analysis, although the statistical significance was lost when K(trans) was averaged over the entire tumor. Collectively these studies suggest that DCEMRI using gadopentetate may have potential clinically, for monitoring inhibition of VEGF signaling in solid tumors.

Averaging keyhole pulse sequence with presaturation pulses and EXORCYCLE phase cycling for dynamic contrast-enhanced MRI.

The purpose of this study was to design a keyhole pulse sequence for quantitative 2D dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) based on a spoiled gradient echo T1-weighted acquisition. Saturation recovery was applied to achieve a linear correlation between signal intensity and contrast agent concentration in an arterial input function (AIF) while simultaneously removing time-of-flight effect. To remove ghosting artifacts arising from incomplete presaturation, EXORCYCLE phase cycling with averaging was applied to the pulse sequence. RF spoiling by radiofrequency switching with the synthesizer can be combined with EXORCYCLE phase cycling. Images affected by the large difference in signal intensity before and after contrast agent administration with the keyhole technique were improved by interleaving of peripheral lines of k-space with groups of central lines. Both peripheral and central lines were renewed during the dynamic scan. AIFs were obtained from the rat abdominal aorta with this keyhole sequence.

Phase I expansion and pharmacodynamic study of the oral MEK inhibitor RO4987655 (CH4987655) in selected patients with advanced cancer with RAS-RAF mutations.

PURPOSE: This phase I expansion study assessed safety, pharmacodynamic effects, and antitumor activity of RO4987655, a pure MEK inhibitor, in selected patients with advanced solid tumor. EXPERIMENTAL DESIGN: We undertook a multicenter phase I two-part study (dose escalation and cohort expansion). Here, we present the part 2 expansion that included melanoma, non-small cell lung cancer (NSCLC), and colorectal cancer with oral RO4987655 administered continuously at recommended doses of 8.5 mg twice daily until progressive disease (PD). Sequential tumor sampling investigated multiple markers of pathway activation/tumor effects, including ERK phosphorylation and Ki-67 expression. BRAF and KRAS testing were implemented as selection criteria and broader tumor mutational analysis added. RESULTS: Ninety-five patients received RO4987655, including 18 BRAF-mutant melanoma, 23 BRAF wild-type melanoma, 24 KRAS-mutant NSCLC, and 30 KRAS-mutant colorectal cancer. Most frequent adverse events were rash, acneiform dermatitis, and gastrointestinal disorders, mostly grade 1/2. Four (24%) of 17 BRAF-mutated melanoma had partial response as did four (20%) of 20 BRAF wild-type melanoma and two (11%) of 18 KRAS-mutant NSCLC. All KRAS-mutant colorectal cancer developed PD. Paired tumor biopsies demonstrated reduced ERK phosphorylation among all cohorts but significant differences among cohorts in Ki-67 modulation. Sixty-nine percent showed a decrease in fluorodeoxyglucose uptake between baseline and day 15. Detailed mutational profiling confirmed RAS/RAF screening and identified additional aberrations (NRAS/non-BRAF melanomas; PIK3CA/KRAS colorectal cancer) without therapeutic implications. CONCLUSIONS: Safety profile of RO4987655 was comparable with other MEK inhibitors. Single-agent activity was observed in all entities except colorectal cancer. Evidence of target modulation and early biologic activity was shown among all indications independent of mutational status. Clin Cancer Res; 20(16); 4251-61. ©2014 AACR.

First-in-human, phase I dose-escalation study of the safety, pharmacokinetics, and pharmacodynamics of RO5126766, a first-in-class dual MEK/RAF inhibitor in patients with solid tumors.

PURPOSE: This phase I study assessed the maximum tolerated dose (MTD), dose-limiting toxicities (DLT), safety, pharmacokinetics, pharmacodynamics, and clinical activity of the first-in-class dual MEK/RAF inhibitor, RO5126766. EXPERIMENTAL DESIGN: Initial dose-escalation was conducted using once daily dosing over 28 consecutive days in 4-week cycles. Further escalation was completed using 2 intermittent dosing schedules [7 days on treatment followed by 7 days off (7on/7off); 4 days on treatment followed by 3 days off (4on/3off)]. RESULTS: Fifty-two patients received RO5126766 at doses of 0.1 to 2.7 mg once daily, 2.7 to 4.0 mg (4 on/3 off), or 2.7 to 5.0 mg (7 on/7 off). The most common DLTs were elevated creatine phosphokinase (CPK) and blurred vision. The MTD for each dosing schedule was 2.25 mg once daily, 4.0 mg (4 on/3 off), and 2.7 mg (7 on/7 off). The dose/schedule recommended for phase II (RP2D) investigation was 2.7 mg (4 on/3 off). Frequent adverse events included rash-related disorders (94.2%), elevated CPK (55.8%), and diarrhea (51.9%). C(max) occurred 1 to 2 hours after dosing and mean terminal half-life was approximately 60 hours. Pharmacodynamic changes included reduced ERK phosphorylation, an increase in apoptosis in tumor tissue, and a reduction in fluorodeoxyglucose (FDG) uptake after 15 days of dosing. Three partial responses were seen: two in BRAF-mutant melanoma tumors and one in an NRAS-mutant melanoma. CONCLUSION: This first-in-human study shows that oral RO5126766 has manageable toxicity, a favorable pharmacokinetic/pharmacodynamic profile, and encouraging preliminary antitumor activity in this population of heavily pretreated patients, achieving tumor shrinkage in around 40% of patients across all dose levels and all tumor types.

Phase I dose-escalation study of the safety, pharmacokinetics, and pharmacodynamics of the MEK inhibitor RO4987655 (CH4987655) in patients with advanced solid tumors.

PURPOSE: This phase I study of the mitogen-activated protein/extracellular signal-regulated kinase inhibitor RO4987655 (CH4987655) assessed its maximum tolerated dose (MTD), dose-limiting toxicities (DLT), safety, pharmacokinetic/pharmacodynamic profile, and antitumor activity in patients with advanced solid tumors. PATIENTS AND METHODS: An initial dose escalation was conducted using a once-daily dosing schedule, with oral RO4987655 administered at doses of 1.0 to 2.5 mg once daily over 28 consecutive days in 4-week cycles. Doses were then escalated from 3.0 to 21.0 mg [total daily dose (TDD)] using a twice-daily dosing schedule. RESULTS: Forty-nine patients were enrolled. DLTs were blurred vision (n = 1) and elevated creatine phosphokinase (n = 3). The MTD was 8.5 mg twice daily (TDD, 17.0 mg). Rash-related toxicity (91.8%) and gastrointestinal disorders (69.4%) were the most frequent adverse events. The pharmacokinetic profile of RO4987655 showed dose linearity and a half-life of approximately 4 hours. At the MTD, target inhibition, assessed by suppression of extracellular signal-regulated kinase phosphorylation in peripheral blood mononuclear cells, was high (mean 75%) and sustained (90% of time >IC(50)). Of the patients evaluable for response, clinical benefit was seen in 21.1%, including two partial responses (one confirmed and one unconfirmed). 79.4% of patients showed a reduction in fluorodeoxyglucose uptake by positron emission tomography between baseline and day 15. CONCLUSION: In this population of heavily pretreated patients, oral RO4987655 showed manageable toxicity, a favorable pharmacokinetics/pharmacodynamics profile, and promising preliminary antitumor activity, which has been further investigated in specific populations of patients with RAS and/or RAF mutation driven tumors.

Examining the acute effects of cediranib (RECENTIN, AZD2171) treatment in tumor models: a dynamic contrast-enhanced MRI study using gadopentate.

Cediranib (RECENTIN, AZD2171) is a highly potent inhibitor of the tyrosine kinase activity associated with all three vascular endothelial growth factor (VEGF) receptors and is currently in Phase II/III clinical trials. Preclinically, cediranib inhibits VEGF signaling and angiogenesis in vivo and impedes solid tumor growth significantly. Clinically, changes observed using dynamic contrast-enhanced MRI (DCE-MRI) with gadopentate suggest that acute cediranib treatment compromises tumor hemodynamics. In this study, a DCE-MRI baseline scan using gadopentate was performed in nude rats bearing Lovo (human colorectal carcinoma) or C6 (rat glioma) tumors. Cediranib (3 mg/kg per day) or vehicle was then dosed orally (2, 26 and 50 h after the baseline scan; 12 rats per group) and a second scan acquired 2 h after the final dosing event. Mean values for K(trans) (Tofts and Kermode-derived) [Magn Reson Med 17 (1991) 357-67] and the initial area under the gadolinium concentration curve over the first 60 s (iAUC) were reduced significantly following cediranib treatment: K(trans) by 33% (P<.05) in both tumor models and iAUC by 23% (P>.05) and 33% (P>.005) in Lovo and C6, respectively. This is the first preclinical investigation to examine the effect of cediranib treatment on tumors by DCE-MRI with gadopentate.

Misregistration artifacts in image-derived arterial input function in non-echo-planar imaging-based dynamic contrast-enhanced MRI.

PURPOSE: To characterize misregistration artifact in arterial input function (AIF) pixels in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a two-dimensional non-echo-planar imaging (EPI)-based gradient-recalled echo (GRE) sequence. MATERIALS AND METHODS: Dynamic gadopentetate-enhanced MRI was acquired in the rat using a semikeyhole acquisition scheme. The AIF was obtained from abdominal aorta pixels. Different sliding-window reconstruction techniques were applied to determine which lines in a series of the semikeyhole acquisition were associated with the misregistration artifacts. RESULTS: The misregistration along the phase-encoding direction arose when k-space lines were acquired during the rise-time of the aortic gadolinium concentration. The maximum blood concentration of gadolinium estimated from the phase shift calculation agreed with that estimated from dosage. CONCLUSION: AIF misregistration results from a phase shift due to increasing gadolinium concentration in the aorta, and may need to be considered in small animal DCE-MRI studies with a high rate of rise in the AIF in high-field MR applications.

Correlation of MRI biomarkers with tumor necrosis in Hras5 tumor xenograft in athymic rats.

Magnetic resonance imaging (MRI) can measure the effects of therapies targeting the tumor vasculature and has demonstrated that vascular-damaging agents (VDA) induce acute vascular shutdown in tumors in human and animal models. However, at subtherapeutic doses, blood flow may recover before the induction of significant levels of necrosis. We present the relationship between changes in MRI biomarkers and tumor necrosis. Multiple MRI measurements were taken at 4.7 T in athymic rats (n = 24) bearing 1.94 +/- 0.2-cm3 subcutaneous Hras5 tumors (ATCC 41000) before and 24 hours after clinically relevant doses of the VDA, ZD6126 (0-10 mg/kg, i.v.). We measured effective transverse relaxation rate (R2*), initial area under the gadolinium concentration-time curve (IAUGC(60/150)), equivalent enhancing fractions (EHF(60/150)), time constant (K(trans)), proportion of hypoperfused voxels as estimated from fit failures in K(trans) analysis, and signal intensity (SI) in T2-weighted MRI (T(2)W). ZD6126 treatment induced > 90% dose-dependent tumor necrosis at 10 mg/kg; correspondingly, SI changes were evident from T2W MRI. Although R2* did not correlate, other MRI biomarkers significantly correlated with necrosis at doses of > or = 5 mg/kg ZD6126. These data on Hras5 tumors suggest that the quantification of hypoperfused voxels might provide a useful biomarker of tumor necrosis.

Gradient echo MRI characterization of development of atherosclerosis in the abdominal aorta in Watanabe Heritable Hyperlipidemic rabbits.

PURPOSE: The Watanabe Heritable Hyperlipidemic (WHHL) rabbit provides an important model of spontaneous atherosclerosis. With a strain of WHHL rabbits which do not develop abdominal aorta lumen stenosis even with advanced atherosclerosis, we studied the MRI-histology correlation, and the natural progression of atherosclerosis in the abdominal aorta. In addition, intra-reader segmentation repeatability and scan-rescan reproducibility were assessed. METHODS: Two batches of female WHHL rabbits were used. The first batch of 6 rabbits was scanned at 20 weeks old. A second batch of 17 rabbits was scanned at 50 weeks old and then randomly divided into two subgroups: 8 were killed for histologic investigation; 9 were kept alive for follow-up, with repeat scanning a week later to assess scan-rescan reproducibility, and again at 73 weeks old to assess disease progression. MR images were acquired at 4.7 T using a chemical shift selective fat suppression gradient echo with a saturation band suppressing blood signal within the aortic lumen. Five slices per animal were acquired, centered around the renal artery region of the abdominal aorta, with in-plane resolution of 0.195 mm and slice thickness of 3 mm. RESULTS: The coefficient of variation for intra-reader reproducibility for aortic wall thickness measurements was 2.5% for repeat segmentations of the same scans on the same day, but segmentations of these same scans made 8 months later showed a systematic change, suggesting that intra-reader bias as well as increased variability could compromise assessments made over time. Comparative analyses were therefore performed in one postprocessing session. The coefficient of variation for scan-rescan reproducibility for aortic wall thickness was 5.5% for nine pairs of scans acquired a week apart and segmented on the same day. Good MRI-histology correlation was obtained. The MRI-measured mean aortic wall thickness of animals at 20 weeks of age was 76% that of animals at 50 weeks of age (p < 0.001). There was a small increase in aortic wall thickness between 50 and 73 weeks of age, but this was not significant (p > 0.05). The corresponding differences in lumen cross-sectional areas at 20, 50, and 73 weeks of age were not significant. These results were consistent with in-house historical histology data on this strain of rabbits. CONCLUSIONS: High-resolution gradient echo MRI can follow disease progression in the WHHL rabbit spontaneous atherosclerosis disease model.

Effective blood signal suppression using double inversion-recovery and slice reordering for multislice fast spin-echo MRI and its application in simultaneous proton density and T2 weighted imaging.

PURPOSE: To design a multislice double inversion-recovery fast spin-echo (FSE) sequence, with k-space reordered by inversion time at slice position (KRISP) technique, to produce black-blood vessel wall magnetic resonance imaging (MRI). MATERIALS AND METHODS: In this sequence, central k-space sampling for each slice is required at inversion time (TI) of the blood signal. To fill the entire k-space, the peripheral lines are obtained less or greater the TI and using a rotating slice order. Blood flow signal suppression was first evaluated using a phantom. Simulation studies were used to investigate FSE image quality. The final sequence was then applied to the rabbit abdominal aorta MRI at 4.7 T. RESULTS: In the flow phantom study, artifacts from slow-flowing water were substantially reduced by the KRISP technique; residual water spins were dephased by the strong phase-encoding gradient required for peripheral k-space. These dephased spins flowed into the slice plane where the center of k-space was being acquired at the TI of the flowing water signal. Multislice black-blood MR images were successfully obtained in the rabbit abdomen using the sequence with the k-trajectory optimized by the simulation study. CONCLUSION: The KRISP technique was effective both in multislice double inversion-recovery FSE and in blood signal suppression.