Tumor Pharmacokinetics Research Articles

Tumor pharmacokinetics and pharmacodynamics of the CDK4/6 inhibitor ribociclib in patients with recurrent glioblastoma

We conducted a phase Ib study (NCT02345824) to determine whether ribociclib, an inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), penetrates tumor tissue and modulates downstream signaling pathways including retinoblastoma protein (Rb) in patients with recurrent glioblastoma (GBM). Study participants received ribociclib (600mg QD) for 8-21days before surgical resection of their recurrent GBM. Total and unbound concentrations of ribociclib were measured in samples of tumor tissue, plasma, and cerebrospinal fluid (CSF). We analyzed tumor specimens obtained from the first (initial/pre-study) and second (recurrent/on-study) surgery by immunohistochemistry for Rb status and downstream signaling of CDK4/6 inhibition. Participants with Rb-positive recurrent tumors continued ribociclib treatment on a 21-day-on, 7-day-off schedule after surgery, and were monitored for toxicity and disease progression. Three participants with recurrent Rb-positive GBM participated in this study. Mean unbound (pharmacologically active) ribociclib concentrations in plasma, CSF, MRI-enhancing, MRI-non-enhancing, and tumor core regions were 0.337μM, 0.632μM, 1.242nmol/g, 0.484nmol/g, and 1.526nmol/g, respectively, which exceeded the in vitro IC50 (0.04μM) for inhibition of CDK4/6 in cell-free assay. Modulation of pharmacodynamic markers of ribociclib CDK 4/6 inhibition in tumor tissues were inconsistent between study participants. No participants experienced serious adverse events, but all experienced early disease progression. This study suggests that ribociclib penetrated recurrent GBM tissue at concentrations predicted to be therapeutically beneficial. Our study was unable to demonstrate tumor pharmacodynamic correlates of drug activity. Although well tolerated, ribociclib monotherapy seemed ineffective for the treatment of recurrent GBM.

Effect of Size on Solid Tumor Disposition of Protein Therapeutics.

In this study, we evaluated the effect of size on tumor disposition of protein therapeutics, including the plasma and tumor pharmacokinetics (PK) of trastuzumab (∼150 kDa), FcRn-nonbinding trastuzumab (∼150 kDa), F(ab)2 fragment of trastuzumab (∼100 kDa), Fab fragment of trastuzumab (∼50 kDa), and trastuzumab scFv (∼27 kDa) in both antigen (i.e., HER2)-overexpressing (N87) and antigen-nonexpressing (MDA-MB-468) tumor-bearing mice. The observed data were used to develop the maximum tumor uptake versus molecular weight and tumor-to-plasma area under the curve (AUC) ratio versus molecular weight relationships. Comparison of the PK of different sizes of FcRn nonbinding molecules in target-expressing tumor showed that ∼100 kDa is an optimal size to achieve maximum tumor uptake and ∼50 kDa is an optimal size to achieve maximum tumor-to-plasma exposure ratio of protein therapeutics. The PK data were also used to validate a systems PK model for tumor disposition of different-sized protein therapeutics. The PK model was able to predict a priori the PK of all five molecules in both tumor types reasonably well (within 2- to 3-fold). In addition, the model captured the bell-shaped relationships observed between maximum tumor uptake and molecular weight and between tumor-to-plasma AUC ratio and molecular weight. Our results provide an unprecedented insight into the effect of size and target engagement on the tumor PK of protein therapeutics. Our results also provide further validation of the tumor disposition model, which can be used to support discovery, development, and preclinical-to-clinical translation of different sizes of protein therapeutics. SIGNIFICANCE STATEMENT: This article highlights the importance of molecular size and target engagement on the tumor disposition of protein therapeutics. Our results suggest that ∼100 kDa is an optimal size to achieve maximum tumor uptake and ∼50 kDa is an optimal size to achieve maximum tumor-to-plasma exposure ratio for non-FcRn-binding targeted protein therapeutics. We also demonstrate that a systems pharmacokinetics model developed to characterize tumor disposition of protein therapeutics can predict a priori the disposition of different-sized protein therapeutics in target-expressing and target-nonexpressing solid tumors.

Abstract 3870: The addition of CB-839 to temozolomide significantly reduces glioma aspartate and glutamate in an IDH mutated patient derived glioma xenograft model

Abstract Background: IDH mutated gliomas are critically dependent on glutaminase for glutamate biosynthesis. CB-839 is a novel glutaminase-1 inhibitor which has demonstrated efficacy in both genetically engineered and patient derived IDH mutated glioma cells, especially in combination with radiation. These preclinical studies evaluate the pharmacodynamic and pharmacokinetic impact of combining CB-839 with TMZ in patient derived xenograft (PDX) glioma models. Methods: GBM164 is a PDX model derived from an IDH1 mutant, 1p/19q non-codeleted glioma. D- and L-2HG levels in untreated GBM164 tumors were compared to GBM6 tumors (IDH wildtype glioma PDX) by GC/MS. Athymic nude mice bearing GBM164 flank tumors were treated with CB-839 (200 mg/kg PO BID x 9 doses) and/or temozolomide (50 mg/kg PO daily x 5 doses) and sacrificed four hours after the last dose to harvest plasma, normal brain and flank tumor. Tumor metabolomics were assessed by GC/MS. DNA damage signaling in tumors was assessed by Western blotting for KAP1 / Chk1 / Chk2 phosphorylation and H2AX / Rad51. Tumor, plasma and brain pharmacokinetics were assessed by LC/MS/MS. Results: Total 2HG levels in GBM164 were 18-fold higher than GBM6. CB-839 monotherapy reduced tumor glutamate (18% reduction, p = 0.15) and aspartate (30% reduction, p = 0.06) when compared to vehicle, however these changes did not reach statistical significance. The combination of CB-839 and TMZ more significantly reduced both tumor glutamate (30% reduction, p = 0.03) and aspartate (34% reduction, p < 0.001) when compared to TMZ monotherapy. CB-839 did not significantly increase DNA damage compared to vehicle, and the combination of CB-839 and TMZ did not significantly increase DNA damage compared to TMZ monotherapy. The mean tumor: plasma ratios of CB-839 concentrations were 0.68 and 0.58 in mice treated with CB-839 monotherapy and CB-839/TMZ, respectively. The mean brain: plasma ratios of CB-839 concentrations were 0.07 and 0.12 in mice treated with CB-839 monotherapy and CB-839/TMZ, respectively. Conclusion: The addition of CB-839 to TMZ significantly reduces glioma aspartate and glutamate in an IDH1 mutant PDX glioma model, without any impact on DNA damage. Survival studies are in progress to assess the efficacy of CB-839 when used in combination with RT and/or TMZ. Citation Format: Sani Haider Kizilbash, Danielle M. Burgenske, Samuel McBrayer, Sandhya Devarajan, Shiv K. Gupta, Taro Hitosugi, Lihong He, Mark A. Schroeder, Brett L. Carlson, Marina Gelman, Charles A. Kunos, Joel M. Reid, Alex A. Adjei, Jann N. Sarkaria. The addition of CB-839 to temozolomide significantly reduces glioma aspartate and glutamate in an IDH mutated patient derived glioma xenograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3870.

Impact of soft protein interactions on the excretion, extent of receptor occupancy and tumor accumulation of ultrasmall metal nanoparticles: a compartmental model simulation.

Ultrasmall metal nanoparticles (NPs) are next-generation nano-based platforms for in vivo disease diagnosis and treatment. Due to their small size below the kidney filtration threshold and marked resistance to nonspecific serum protein adsorption, ultrasmall NPs can be rapidly excreted through the kidneys and escape liver uptake. However, although ultrasmall particles may be deemed highly resistant to protein adsorption, the real extent of this resistance is not known. Here, a simple compartmental model simulation was therefore implemented to understand how NP behavior in vivo could be modulated by soft, transient NP–plasma protein interactions characterized by dissociation constants in the millimolar range. In Model 1, ultrasmall NPs functionalized with a targeting probe, plasma proteins and target receptors were assumed to co-exist within a single compartment. Simulations were performed to understand the synergistic effect of soft interactions, systemic clearance and NP size on receptor occupancy in the single compartment. The results revealed the existence of a narrow range of ultraweak affinities and optimal particle sizes leading to greater target occupancy. In Model 2, simulations were performed to understand the impact of soft interactions on NP accumulation into a peripheral (tumor) compartment. The results revealed that soft interactions – but not active targeting – enhanced tumor uptake levels when tumor accumulation was limited by ‘fast’ plasma clearance and ‘slow’ vascular extravasation. The simple model presented here provides a basic framework to quantitatively understand the blood and tumor pharmacokinetics of ultrasmall NPs under the influence of transient protein interactions.

Abstract 297: AZD4573: Mechanistic PKPD model linking CDK9 inhibition to Mcl1 depletion and induction of apoptosis in preclinical AML model

Abstract Cyclin-dependent kinase 9 (CDK9) regulates elongation of transcription through phosphorylation of RNA polymerase II (pSer2-RNAPII), and its short-term inhibition results in the selective downregulation of genes with short-lived transcripts and labile proteins - including the anti-apoptotic protein Mcl1. AZD4573 is a selective inhibitor of CDK9 with short pharmacokinetic (PK) half-life. Intermittent dosing of AZD4573 in mouse MV411 (AML cell line) xenograft models results in progressive reduction in tumor volume with the mechanism of action believed to be via induction of apoptosis following depletion of Mcl1. The aim of this work was to derive a quantitative understanding of the relationships between extent and duration of CDK9 inhibition, depletion of Mcl1 and rate of induction of apoptosis in MV411 tumor cells. A mechanistic model has been established that quantitatively and dynamically connects AZD4573 plasma and tumor PK to the rate and extent of modulation of pSer2-RNAPII and Mcl1 in the tumor and rate of induction of cell death (as measured by reduction in tumor volume). Tumor pSer2-RNAPII and Mcl1 pharmacodynamics were modeled using a series of linked indirect response models. Production rate of pSer2-RNAPII was modeled as being directly inhibited by AZD4573 concentration in the tumor. Production rate of Mcl1 was linked to pSer2-RNAPII via a series of transit compartments to capture the transcription/translation driven delay in onset of response. Induction of intrinsic apoptosis in the MV411 tumor cells was modelled as being inhibited by Mcl1. Tumor pSer2-RNAPII exhibited a rapid, dose-dependent decrease following IP dosing of AZD4573 in mice. The free concentration of AZD4573 that resulted in half-maximal inhibition of pSer2-RNAPII production rate was estimated to be in the range 11-21 nM. Following a brief delay, tumor Mcl1 also exhibited a relatively rapid decrease that was proportional to the pSer2-RNAPII response. Mcl1 protein half-life was estimated to be 0.3 hr. Rate of induction of apoptosis could be decribed as a saturable first-order process (Kmax ~ 0.2 hr-1) and appeared to exhibit a steep response to the depletion of Mcl1, with reduction of Mcl1 to 25% (of the baseline value) being estimated to result in half-maximal rate of induction of apoptosis in the MV411 cells. The described MV411 PKPD/efficacy model has been assumed to be representative of AML in human patients and was used to derive preliminary predictions of clinical efficacy at a range of possible IV dosing regimens. Citation Format: Douglas Ferguson, Theresa Proia, Justin Cidado, Scott Boiko, Maryann San Martin, Steven Criscione, Wenlin Shao, Lisa Drew. AZD4573: Mechanistic PKPD model linking CDK9 inhibition to Mcl1 depletion and induction of apoptosis in preclinical AML model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 297.

Abstract 4926: Preclinical intratumoral pharmacokinetics (PK) of capecitabine (Cap) given +/- eribulin (Eri)

Abstract Background: Eri & Cap are active as single agents in metastatic breast cancer, but the combination appears particularly active & well tolerated clinically. We explored the hypothesis that normalisation of tumor vasculature by Eri seen in preclinical models may enhance delivery of Cap to the tumor when given in combination. Methods: Mice bearing MDA-MD-231 xenografts were treated with Cap 540mg/kg p.o. day 1 alone or following Eri 1mg/kg i.v. on day -8 then sacrificed on day 1 at 15min, 30min, 1h, 2h, 4h, 6h or 24h after Cap (n=3/ time point). Concentrations of Cap & its metabolites (5'-deoxy-5-fluorocytidine, 5DFCR; 5-Fluoro-5'-deoxyuridine, 5DFUR; 5-Fluorouracil, 5FU; 5-Fluorouridine, 5FUrd; & 5-Fluoro-2'-deoxyuridine, 5FdUrd) in plasma, tumor, skin & muscle were analysed by LC-MS/MS. Half the tumor was reserved to study Cap distribution using matrix-assisted laser desorption/ionization mass spectrometry imaging with haem imaged as a surrogate marker for tumour vasculature. Results: We found no differences in the plasma, skin, muscle or tumor PK profiles of Cape & its metabolites with the addition of Eri (Table 1). In both treatment arms intratumoral concentrations of 5DFUR, 5FU, 5FUrd & 5FdUrd appeared higher in tumors while those of Cape & 5DFCR appeared higher in normal healthy tissues. To mitigate the variability in tumor Cape concentrations between animals, we also expressed the results as the ratio of drug concentration in tumour:healthy tissue but again found no apparent effect of Eri on intratumoral drug concentrations. Analyses of drug distribution are on-going & will be presented. Conclusion: No clear effect of Eri on intratumoral concentrations of Cape or its metabolites was seen. We are exploring potential differences in tumour drug distribution. Citation Format: Maria Jove Casulleras, Jade Spencer, Paul Loadman, Malcolm Clench, Steve Shnyder, Patricia Cooper, Cristina Russo, Amanda Race, Ramon Salazar, Chris Twelves. Preclinical intratumoral pharmacokinetics (PK) of capecitabine (Cap) given +/- eribulin (Eri) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4926.

Hepatocellular carcinoma-targeted nanoparticles for cancer therapy.

Nanocarriers, such as liposomes, have the potential to increase the payload of chemotherapeutic drugs while decreasing toxicity to non-target tissues; such advantageous properties can be further enhanced through surface conjugation of nanocarriers with targeting moieties. We previously reported that SP94 peptides, identified by phage display, exhibited higher binding affinity to human hepatocellular carcinoma (HCC) than to hepatocytes and other normal cells. Here, we confirm the tumor-targeting properties of SP94 peptide by near-infrared fluorescence imaging. Non-targeted PEGylated liposomal doxorubicin (LD) and SP94-conjugated PEGylated liposomal doxorubicin (SP94-LD) were compared by assessing pharmacokinetics, tissue distribution, and antitumor efficacy in xenograft-bearing mice, in order to investigate the effectiveness of SP94-mediated targeting for cancer therapy. SP94-LD demonstrated a significant increase in drug accumulation in tumors, while its plasma residence time was the same as its non-targeted equivalent. Consistent with this result, conjugation of targeting peptide SP94 enhances the therapeutic efficacy of liposomal doxorubicin in mouse models with hepatocellular carcinoma xenografts. Furthermore, combination targeted therapy exhibited a significant enhancement against orthotopic tumor growth, and markedly extended the survival of mice compared with all other treatments. Our study shows that SP94-mediated targeting enhances antitumor efficacy by improving tumor pharmacokinetics and tissue distribution, allowing large amounts of antitumor drugs to accumulate in tumors.

ACTR-67. PLASMA AND TUMOR PHARMACOKINETICS OF RIBOCICLIB IN PATIENTS WITH RECURRENT GLIOBLASTOMA

BACKGROUND CDK4/6-dependent cell-cycle regulation is disrupted in 78% of glioblastoma (GBM) patients and novel CDK4/6 inhibitors have shown anti-tumor activity in animal models. To explore the utility of ribociclib, a selective CDK4/6-inhibitor, in treating recurrent GBM patients, we conducted a phase 0/II clinical trial ({type:clinical-trial,attrs:{text:NCT02933736,term_id:NCT02933736}}NCT02933736) to examine plasma and tumor pharmacokinetics (PK) and pharmacodynamics (PD).

ACTR-16. RESULTS OF THE OPARATIC TRIAL: A PHASE I DOSE ESCALATION STUDY OF OLAPARIB IN COMBINATION WITH TEMOZOLOMIDE (TMZ) IN PATIENTS WITH RELAPSED GLIOBLASTOMA (GBM)

2022Background: Olaparib, a small molecule inhibitor of poly (ADP-ribose) polymerase (PARP), may improve GBM outcomes by enhancing cytotoxic effects of ionising radiation and TMZ. Clinical development of PARP inhibitors has been restricted by exacerbation of hematological toxicity. We investigated tumor pharmacokinetics (PK) of olaparib and safety and tolerability of its combination with TMZ. Methods: Dose escalation explored different schedules of olaparib (tablet formulation) with 42 day cycles of daily low dose TMZ. A dose expansion cohort evaluated the maximum tolerated schedule. PK analysis was performed on tumor and blood samples from patients undergoing neurosurgical resection, who received 4 olaparib doses pre-operatively. Results: 48 patients were recruited (median age 51(18-68); 29 male, 19 female) of whom 27 underwent surgery and 35 received olaparib/TMZ and were evaluable. 13 evaluable patients received expansion dose schedule (median age 54(21-67); 9 male, 4 female). Olaparib was detected in ...

Hydroxycamptothecin liposomes based on thermal and magnetic dual-responsive system: preparation, in vitro and in vivo antitumor activity, microdialysis-based tumor pharmacokinetics

Due to the absence of lactone form of hydroxycamptothecin, the commercially available hydroxycamptothecin injection exhibits inefficient therapeutic effects. In this study, we constructed a novel delivery system (thermosensitive magnetic liposomes) that protects lactone form of hydroxycamptothecin from blood or water. After hydroxycamptothecin was loaded into the thermosensitive magnetic liposome (HCPT/TML), its in vitro and in vivo antitumor activity and microdialysis-based tumour pharmacokinetics were determined. The results demonstrated that HCPT/TMLs possessed favourable physicochemical features and significant cytotoxicity against the Huh-7 cells in vitro. In the in vivo antitumor study and tumour pharmacokinetics, HCPT/TMLs displayed effective targeting delivery and antitumor effects, which corresponded to the determined hydroxycamptothecin concentration in tumour tissue. In conclusion, this thermal and magnetic dual-responsive system can efficiently deliver hydroxycamptothecin to tumour tissue and has great potential application in cancer treatment.

Development and Evaluation of 18F-IRS for Molecular Imaging Mutant EGF Receptors in NSCLC

To prepare and evaluate a new radiotracer 18F-IRS for molecular imaging mutant EGF Receptors in vitro and vivo. Uptake and efflux of 18F-IRS were performed with four NSCLC cell lines including HCC827, H1975, H358 and H520. In vivo tumor targeting and pharmacokinetics of the radiotracers were also evaluated in HCC827, H1975, H358 and H520 tumor-bearing nude mice by PET/CT imaging. Ex vivo biodistribution assays were performed to quantify the accumulation of 18F-IRS in vivo. We also performed 18F-IRS PET/CT imaging of three patients with NSCLC. We labeled this small molecule with QD620 for flow cytometry and confocal imaging analyses. The uptakes of 18F-IRS by HCC827 and HCC827 tumors were significantly higher than those of H358, H1975 and H520, and they were reduced by the addition of 100 μM of gefitinib. Biodistribution experiments showed an accumulation of 18F-IRS in tumors of HCC827 xenografts. Flow cytometry and confocal imaging with QD620-IRS further demonstrated that binding specifically to HCC827 cells. 18F-IRS accumulation was preferential in the tumor, which was NSCLC with responsive EGFR exon 19 deleted. 18F-IRS showed high binding stability and specificity to 19 exon deleted EGFR mutation in vitro and vivo.

Results of the OPARATIC trial: A phase I dose escalation study of olaparib in combination with temozolomide (TMZ) in patients with relapsed glioblastoma (GBM).

2022 Background: Olaparib, a small molecule inhibitor of poly (ADP-ribose) polymerase (PARP), may improve GBM outcomes by enhancing cytotoxic effects of ionising radiation and TMZ. Clinical development of PARP inhibitors has been restricted by exacerbation of hematological toxicity. We investigated tumor pharmacokinetics (PK) of olaparib and safety and tolerability of its combination with TMZ. Methods: Dose escalation explored different schedules of olaparib (tablet formulation) with 42 day cycles of daily low dose TMZ. A dose expansion cohort evaluated the maximum tolerated schedule. PK analysis was performed on tumor and blood samples from patients undergoing neurosurgical resection, who received 4 olaparib doses pre-operatively. Results: 48 patients were recruited (median age 51(18-68); 29 male, 19 female) of whom 27 underwent surgery and 35 received olaparib/TMZ and were evaluable. 13 evaluable patients received expansion dose schedule (median age 54(21-67); 9 male, 4 female). Olaparib was detected in 73 of 74 tumor core specimens from 27 patients; mean conc. 588nM (97-1374nM), and in 27 of 28 tumor margin specimens from 10 patients; mean conc. 500nM (97-1237nM). Margin: core ratios ranged from 0.2–3.9(mean 1.2); tumor: plasma ratios ranged from 0.01 to 0.9 (mean 0.25). Olaparib dosing on days 1-5 was hindered by myelosuppression. Expansion cohort dose was defined as TMZ 75 mg/m2daily plus olaparib 150 mg (OD) days 1-3 weekly. Of 13 evaluable patients receiving expansion dose-schedule, 9 completed cycle 1, 2 completed cycle 2 and 2 completed cycle 3. Currently 45% of the evaluable patients remain progression-free at 6 months, with 2 still on treatment (full data set May2017). Of 35 evaluable patients, 24 experienced AE Grade ≥3 (see Table). Conclusions: Olaparib penetrates both core and margins of recurrent GBM despite failing to penetrate the intact brain barrier in pre-clinical heathy rodent models. Combination with extended low dose TMZ is safe and well tolerated, yielding encouraging 6 month progression-free survival rates. Clinical trial information: NCT01390571. [Table: see text]

Fasting protects against the side effects of irinotecan treatment but does not affect anti-tumour activity in mice.

The main limitation to the use of irinotecan in the treatment of colorectal cancer is the severity of side effects, including neutropaenia and diarrhoea. Here, we explored the effects of 3 days of fasting on irinotecan-induced toxicities, on plasma, liver and tumour pharmacokinetics and on anti-tumour activity in mice. Male BALB/c mice received C26 colon carcinoma cells subcutaneously. They were randomized 1:1 into equally sized ad libitum fed and fasted groups after which they were treated with irinotecan. Weight and adverse side effects were recorded daily. At the end of the experiment, tumours were resected and weighed, and concentrations of irinotecan and its active metabolite SN-38 were determined in plasma and tumour. Fasting prevented the diarrhoea and visible signs of discomfort induced by irinotecan. Ad libitum fed animals developed leucopenia compared with untreated controls, whereas fasted mice did not. Irinotecan suppressed tumour growth equally in both treated groups, compared with untreated controls. Levels of the active irinotecan metabolite SN-38 9 (calculated as AUC values) were significantly lower in fasted mice in both plasma and liver, but not in tumour tissue. Fasting protected against irinotecan-induced side effects without interfering with its anti-tumour efficacy. Fasting induced a lower systemic exposure to SN-38, which may explain the absence of adverse side effects, while tumour levels of SN-38 remained unchanged. These data offer important new approaches to improve treatment with irinotecan in patients.

NKTR-214, an Engineered Cytokine with Biased IL2 Receptor Binding, Increased Tumor Exposure, and Marked Efficacy in Mouse Tumor Models.

Aldesleukin, recombinant human IL2, is an effective immunotherapy for metastatic melanoma and renal cancer, with durable responses in approximately 10% of patients; however, severe side effects limit maximal dosing and thus the number of patients able to receive treatment and potential cure. NKTR-214 is a prodrug of conjugated IL2, retaining the same amino acid sequence as aldesleukin. The IL2 core is conjugated to 6 releasable polyethylene glycol (PEG) chains. In vivo, the PEG chains slowly release to generate active IL2 conjugates. We evaluated the bioactivity and receptor binding of NKTR-214 and its active IL2 conjugates in vitro; the tumor immunology, tumor pharmacokinetics, and efficacy of NKTR-214 as a single agent and in combination with anti-CTLA-4 antibody in murine tumor models. Tolerability was evaluated in non-human primates. In a murine melanoma tumor model, the ratio of tumor-killing CD8(+) T cells to Foxp3(+) regulatory T cells was greater than 400 for NKTR-214 compared with 18 for aldesleukin, supporting preferential activation of the IL2 receptor beta over IL2 receptor alpha, due to the location of PEG molecules. NKTR-214 provides a 500-fold greater exposure of the tumor to conjugated IL2 compared with aldesleukin. NKTR-214 showed efficacy as a single agent and provided durable immunity that was resistant to tumor rechallenge in combination with anti-CTLA-4 antibody. NKTR-214 was well tolerated in non-human primates. These data support further evaluation of NKTR-214 in humans for a variety of tumor types, adding to the repertoire of potent and potentially curative cancer immunotherapies.

Abstract C197: Accurins improve the pharmacokinetics, pharmacodynamics, tolerability and anti-tumor activity of the AKT inhibitor MK-2206

Abstract Background: BIND-2206 Accurins are novel polymeric nanoparticles encapsulating MK-2206, a Merck AKT inhibitor in phase 2 trials. MK-2206 targets the phosphatidylinositol 3-kinase (PI3K) pathway via AKT inhibition and has demonstrated therapeutic efficacy in the treatment of cancer albeit with dose limiting toxicities. Accurins have shown promise for targeting oncology agents preferentially to tumors, while limiting systemic exposure. To determine if encapsulation of MK-2206 improves therapeutic index, studies were performed to evaluate pharmacokinetics (PK), pharmacodynamics (PD), tolerability and anti-tumor activity compared to parent MK-2206. Materials and Methods: PK of four Accurin formulations with varying in vitro drug release rates was evaluated. Based on these data, two lead Accurins (BIND-2206C and BIND-2206D) were selected for further characterization. Since AKT inhibitors are documented to induce hyperglycemia in mice, blood glucose levels were also evaluated after acute administration of BIND-2206 Accurins or parent MK-2206 as a measure of tolerability. Using a panel of human tumor xenografts (VCaP, SK-OV-3 and BT-474) anti-tumor activity of the Accurins was assessed in mice. When tumors were established mice were dosed orally with parent MK-2206 or intravenously with BIND-2206 Accurins two or three times per week on a three week cycle. Tumor volume was measured post treatment to determine anti-tumor activity. Following final drug administration, tumors were collected for PK and PD evaluation. Extent and duration of tumor target inhibition was evaluated by measuring pAKT and total AKT using a mesoscale discovery method and was correlated to tumor MK-2206 levels. Results: Accurins BIND-2206C and BIND-2206D significantly enhanced the PK profile of parent MK-2206 by increasing Cmax (33 fold) and AUC (222 fold) and decreasing clearance (38 fold) in mice. In addition, both BIND-2206 Accurins improved tolerability as demonstrated by no hyperglycemic response compared to a 300% increase in blood glucose in nude mice treated with parent MK-2206. In the VCaP human prostate cancer tumor model, BIND-2206C inhibited tumor growth by 88% and BIND-2206D induced 16% tumor regression showing significant enhancement of anti-tumor efficacy compared to 55% tumor growth inhibition achieved by parent MK-2206. This correlated with high tumor exposure at 72 hours and prolonged tumor PD at 96 hours post dose for both Accurins compared to parent MK-2206. A similar increase in tumor exposure and prolonged PD response resulted in enhanced anti-tumor efficacy for BIND-2206 Accurins in the SK-OV-3 human ovarian cancer tumor model. In the BT-474 HER2 over-expressing human breast cancer tumor model, BIND-2206 Accurins did not improve efficacy compared to parent drug, although there was significant and prolonged tumor PD correlating with enhanced tumor PK. This suggests that anti-tumor efficacy is model specific and a combination strategy in the BT-474 model may be advantageous. Conclusions: BIND-2206 Accurins showed differentiated PK, increased tumor exposure, prolonged duration of target inhibition, superior efficacy and enhanced tolerability compared to parent MK-2206. These data suggest that nanoparticle formulations of the AKT inhibitor, MK-2206, may provide improved tolerability and therapeutic efficacy in a clinical setting. Citation Format: Louise Cadzow, Michael H. Lam, Young Ho Song, Maria Figueiredo, Hong Wang, David De Witt, Vincenzo Pucci, Jan-Rung Mo, Eric Lewis-Clark, Heidi Ferguson, Marian Gindy, Susan Low, Steve Zale, Jeff Hrkach, Caroline McGregor, Brian J. Long. Accurins improve the pharmacokinetics, pharmacodynamics, tolerability and anti-tumor activity of the AKT inhibitor MK-2206. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C197.

NKTR-102 Efficacy versus irinotecan in a mouse model of brain metastases of breast cancer.

BackgroundBrain metastases are an increasing problem in women with invasive breast cancer. Strategies designed to treat brain metastases of breast cancer, particularly chemotherapeutics such as irinotecan, demonstrate limited efficacy. Conventional irinotecan distributes poorly to brain metastases; therefore, NKTR-102, a PEGylated irinotecan conjugate should enhance irinotecan and its active metabolite SN38 exposure in brain metastases leading to brain tumor cytotoxicity.MethodsFemale nude mice were intracranially or intracardially implanted with human brain seeking breast cancer cells (MDA-MB-231Br) and dosed with irinotecan or NKTR-102 to determine plasma and tumor pharmacokinetics of irinotecan and SN38. Tumor burden and survival were evaluated in mice treated with vehicle, irinotecan (50 mg/kg), or NKTR-102 low and high doses (10 mg/kg, 50 mg/kg respectively).ResultsNKTR-102 penetrates the blood-tumor barrier and distributes to brain metastases. NKTR-102 increased and prolonged SN38 exposure (>20 ng/g for 168 h) versus conventional irinotecan (>1 ng/g for 4 h). Treatment with NKTR-102 extended survival time (from 35 days to 74 days) and increased overall survival for NKTR-102 low dose (30 % mice) and NKTR-102 high dose (50 % mice). Tumor burden decreased (37 % with 10 mg/kg NKTR-102 and 96 % with 50 mg/kg) and lesion sizes decreased (33 % with 10 mg/kg NKTR-102 and 83 % with 50 mg/kg NKTR-102) compared to conventional irinotecan treated animals.ConclusionsElevated and prolonged tumor SN38 exposure after NKTR-102 administration appears responsible for increased survival in this model of breast cancer brain metastasis. Further, SN38 concentrations observed in this study are clinically achieved with 145 mg/m2 NKTR-102, such as those used in the BEACON trial, underlining translational relevance of these results.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1672-4) contains supplementary material, which is available to authorized users.

Abstract 4517: Plasma and tumor pharmacokinetics of IV LMP744, a novel indenoisoquinoline topoisomerase I inhibitor, in a canine phase I study

Abstract Introduction: LMP744 (NSC706744) is one of 3 indenoisoquinolines being evaluated in pet dogs with lymphoma to define their safety, pharmacokinetics, and pharmacodynamic modulation (COTC007b). LMP744 forms stable DNA-topoisomerase I (Top1) cleavage complexes and induces unique DNA cleavage sites relative to approved Top1 poisons; LMP744 is not a substrate for ABC transporters and does not have the stability issues inherent to camptothecins. Here we report the plasma and tumor pharmacokinetics of LMP744 administered IV daily x 5 to patient dogs. Methods: Eligibility included: dogs >15 kg with histologically confirmed non-Hodgkin's lymphoma with nodal presentation (stage 2 or greater) and minimal nodes size for biopsy of 3 cm in the longest dimension, performance status of Grade 0 or 1 and informed owner consent. Dose levels (DL) explored were 25, 50, 75, 100, and 125 mg/m2/day through a 3+3 dose escalation study design. LMP744 was administered over 1 h IV daily x 5, Q28D. LMP744 was quantitated with a validated LC-MS/MS assay, and plasma pharmacokinetic parameters determined non-compartmentally with PK Solutions and plasma and tumor parameters compartmentally with ADAPT5 through iterated two stage (ITS) and maximum likelihood solution with the expectation maximization algorithm (MLEM). Results: All 18 dogs had useable pharmacokinetic data. Non-compartmental analysis suggested linear relationships between plasma Cmax and tumor C2h vs. dose. LMP744 distributed extensively to tumor tissue and mean tumor concentrations were at least 2 orders of magnitude higher than plasma concentrations at equivalent time points of 2, 6 and 120 h. Compartmental modeling with a 3 compartment linear model resulted in a good fit to the plasma data. The parameters and%CVs respectively for Clt, Vc, Cld1, Vp1, Cld2, Vp2 were 57.5 L/h/m2 (29%), 136 L/m2 (24%), 234 L/h/m2 (24%), 1180 L/m2 (27%), 30.8 L/h/m2 (63%), 5140 L/m2 (67%). Sequential plasma half-lives were 16.5 min, 13 h, and 183 (31%) h, respectively. In line with the long t1/2, plasma accumulation was observed on this daily times-5 schedule. Conclusion: The plasma pharmacokinetics of LMP744 in dogs display triphasic behavior, a relatively high total body clearance at 57.5 L/h/m2, and a terminal half-life of 183 h. The favorable biodistribution to tumor may be a valuable distinction to consider in the translation of this novel indenoisoquinoline to the clinic. Support: N01-CM-2011-00015, N01-CM-42202 and P30-CA-47904 Note: This abstract was not presented at the meeting. Citation Format: Julie L. Eiseman, Julianne Holleran, David L. McCormick, Miguel Muzzio, Joseph M. Covey, Chand Khanna, Christina Mazcko, Yves Pommier, Melissa Paolini, Amy Leblanc, Jenna H. Burton, James H. Doroshow, Joseph E. Tomaszewski, Jan H. Beumer. Plasma and tumor pharmacokinetics of IV LMP744, a novel indenoisoquinoline topoisomerase I inhibitor, in a canine phase I study. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4517. doi:10.1158/1538-7445.AM2015-4517

Abstract A95: Local iontophoretic delivery of FOLFIRINOX minimizes systemic toxicity for the treatment of pancreatic cancer

Abstract Systemic toxicity and poor delivery of many cytotoxic agents restrict their utility in the treatment of pancreatic cancer. Newer drug regimens, such as FOLFIRINOX, are limited to patients with the best performance status due to substantial toxicity. In an attempt to mitigate systemic toxicity, improve delivery and thus the efficacy of cytotoxic agents, we have developed modalities for the localized iontophoretic delivery of cytotoxic agents to primary pancreatic tumors. Iontophoretic delivery of mitomycin C, dexamethasone, and lidocaine have been successfully implemented for bladder cancer, anterior uveitis, and regional anesthesia. We initially evaluated the local iontophoretic device delivery of gemcitabine (GEM) to orthotopic patient-derived xenograft (PDX) models of pancreatic cancer. Devices were surgically implanted when tumors reached a median volume of 200 mm3, as determined by high-resolution 3D ultrasound. High-performance liquid chromatography (LC) analysis of the tumors directly after a single treatment showed a mean concentration of 229.4±233.0 µg/g for device delivery compared to 19.4±15.9 µg/g for intravenous (IV) delivery. Tumor pharmacokinetics (PK) as measured by area under the curve (AUC) was 384.1 hr*µg/g for device and 30.8 hr*µg/g for IV delivery; plasma GEM AUC was undetectable for device and 65.2 hr*µg/mL for IV delivery. To evaluate the tumor response to device delivery of GEM (DEVGEM), twice weekly treatments were administered for 7 weeks. DEVGEM resulted in significant tumor regression in 7 of 7 mice, outperforming IVGEM and the control arms of IV and device saline. Mice treated with DEVGEM had a mean log2-fold change in tumor volume of -0.8 compared to a mean log2-fold change in tumor volume of 1.1 for IVGEM, 3.0 for IV saline, and 2.6 for device saline groups (p < 0.01). DEVGEM was better tolerated based on greater body weight gain compared to IVGEM with minimal changes in alanine transaminase and lipase. Overall, DEVGEM resulted in tumor regression in 7/7 mice compared to no regression (0/7) in the IVGEM group while maintaining low systemic exposure of GEM. The safe and effective delivery of GEM in the PDX models supported the extension of this delivery modality to the more effective, but highly toxic regimen of FOLFIRINOX. Dose toxicity studies in mice were performed and IV dosing of FOLFIRINOX was determined. A doublet regimen (oxaliplatin (OX)/leucovorin (LV) followed by fluorouracil (FU)/irinotecan(IRI)), which leverages the potentiation of FU activity by LV and possible enhancement of IRI activity by OX, was used for both device and IV delivery. To evaluate the PK of device delivery of FOLFIRINOX, devices were implanted in PDX mice and a single treatment was administered. LC- and inductively coupled plasma-mass spectrometry analysis of the tumors directly after the treatment revealed a 33-fold greater concentration of FU (261.1±321.5 vs 8.0±2.1 µg/g), 31-fold greater concentration of OX (15.6±7.6 vs 0.5±0.3 µg/g), and 3-fold greater concentration of IRI (21.7±9.3 vs 7.2±1.9 µg/g) for device delivery compared to IV FOLFIRINOX. Analysis of plasma, pancreas, liver, and kidney showed significantly lower concentrations of drugs after device delivery compared to IV delivery, suggesting that device delivery of FOLFIRINOX will have minimal systemic toxicity. Long-term therapeutic studies in orthotopic PDX models of pancreatic cancer are ongoing. The local iontophoretic delivery of chemotherapeutics, especially FOLFIRINOX, has the potential to surpass conventional techniques of treatment by driving cytotoxic therapies directly into the tissue. This has potential paradigm shifting implications for the treatment of pancreatic cancer for patients with unresectable non-metastatic disease, palliation of local symptoms, and may be considered as a neoadjuvant modality prior to surgery. Citation Format: James D. Byrne, Mohammed R. Jajja, Allison N. Schorzman, Amanda W. Keeler, Adrian T. O'Neill, James C. Luft, William C. Zamboni, Joseph M. DeSimone, Jen Jen Yeh. Local iontophoretic delivery of FOLFIRINOX minimizes systemic toxicity for the treatment of pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A95.

High-resolution MRI analysis of breast cancer xenograft on the chick chorioallantoic membrane.

The chick chorioallantoic membrane (CAM) model has been successfully used to study angiogenesis, cancer progression and its pharmacological treatment, tumor pharmacokinetics, and properties of novel nanomaterials. MRI is an attractive technique for non-invasive and longitudinal monitoring of physiological processes and tumor growth. This study proposes an age-adapted cooling regime for immobilization of the chick embryo, enabling high-resolution MRI of the embryo and the CAM tumor xenograft. 64 chick embryos were enrolled in this study. The novel immobilization and imaging protocol was optimized in 29 embryos. From d7 to d18 immobilization of the embryo up to 90 min was achieved by cooling at 4 °C pre-imaging, with cooling times adapted to age. Its application to tumor growth monitoring was evaluated in 15 embryos after xenotransplantation of human MDA-MB-231 breast cancer cells on CAM. Tumor volumes were monitored from d4 to d9 after grafting (d11 to d16 after incubation) applying a T2 -weighted multislice RARE sequence. At d9 after grafting, the tumors were collected and compared with the MRI-derived data by histology and weight measurements. Additional imaging methods comprising DWI, T2 mapping, and the bio-distribution of contrast agents were tested at d9 after grafting in 20 further embryos. With the adaptive cooling regime, motion artifacts could be completely avoided for up to 90 min scan time, enabling high-resolution in ovo imaging. Excellent anatomical details could be obtained in the embryo and tumors. Tumor volumes could be quantified over time. The results prove the feasibility of high-resolution MRI for longitudinal tumor and organ growth monitoring. The suggested method is promising for future applications such as testing tailored and/or targeted treatment strategies, longitudinal monitoring of tumor development, analysis of therapeutic efficacies of drugs, or assessment of tumor pharmacokinetics. The method provides an alternative to animal experimentation.

Are capecitabine and the active metabolite 5-Fu CNS penetrable to treat breast cancer brain metastasis?

Brain metastasis (BM) is increasingly diagnosed in Her2 positive breast cancer (BC) patients. Lack of effective treatment to breast cancer brain metastases (BCBMs) is probably due to inability of the current therapeutic agents to cross the blood-brain barrier. The central nervous system (CNS) response rate in BCBM patients was reported to improve from 2.6%-6% (lapatinib) to 20%-65% (lapatinib in combination with capecitabine). Lapatinib is a poor brain penetrant. In this study, we evaluated the CNS penetration of capecitabine and hoped to interpret the mechanism of the improved CNS response from the pharmacokinetic (PK) perspective. Capecitabine does not have antiproliferative activity and 5-fluorouracil (5-FU) is the active metabolite. Capecitabine was orally administered to mouse returning an unbound brain-to-blood ratio (Kp,uu,brain) at 0.13 and cerebrospinal fluid (CSF)-to-unbound blood ratio (Kp,uu,CSF) at 0.29 for 5-FU. Neither free brain nor CSF concentration of 5-FU can achieve antiproliferative concentration for 50% of maximal inhibition of cell proliferation of 4.57 µM. BCBM mice were treated with capecitabine monotherapy or in combination with lapatinib. The Kp,uu,brain value of 5-FU increased to 0.17 in the brain tumor in the presence of lapatinib, which is still far below unity. The calculated free concentration of 5-FU and lapatinib in the brain tumor did not reach the antiproliferative potency and neither treatment showed antitumor activity in the BCBM mice. The CNS penetration of 5-FU in human was predicted based on the penetration in preclinical brain tumor, CSF, and human PK and the predicted free CNS concentration was below the antiproliferative potency. These results suggest that CNS penetration of 5-FU and lapatinib are not desirable and development of a true CNS penetrable therapeutic agent will further improve the response rate for BCBM.