SN-38 Concentrations Research Articles

Effect of UGT1A1, CYP3A and CES Activities on the Pharmacokinetics of Irinotecan and its Metabolites in Patients with UGT1A1 Gene Polymorphisms.

Irinotecan (CPT-11) is metabolized to an active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38) by carboxylesterase (CES). SN-38 is then converted to the inactive metabolite SN-38 glucuronide (SN-38G) by glucuronosyltransferase 1A1 (UGT1A1). Genetic polymorphisms in UGT1A1 have been associated with altered SN-38 pharmacokinetics, which increase the risk of toxicity in patients. CPT-11 is also converted to 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin (APC) and 7-ethyl-10-(4-amino-1-piperidino) carbonyloxycamptothecin (NPC) by cytochrome P450 3A (CYP3A), and this route also affects the plasma concentration of SN-38. We evaluated the activities of UGT1A1, CYP3A, and CES and the factors affecting the pharmacokinetics of plasma SN-38 in patients with UGT1A1 gene polymorphisms. Three male patients aged 56, 65, and 49 years were recruited for the analysis. All patients had pancreatic cancer, received FOLFIRINOX, and had UGT1A1*6/*6 (patients 1 and 3) or *6/*28 (patient 2) genetic polymorphisms. The rate constants for evaluating the enzyme activity were determined from the measured plasma concentration of CPT-11 and its metabolites using a two-compartment model by WinNonlin. The area under the plasma concentration-time curve (AUC) of SN-38 was patient 1 > patient 2 > patient 3. The rate constants obtained from the model analysis indicated the respective enzyme activities of UGT1A1 (k57), CYP3A (k13 + k19), and CES (k15). The order of values for UGT1A1 activity was patient 2 > patient 3 > patient 1. Since UGT1A1 activity was low in patient 1 with a high AUC of SN-38, it can be said that the increase in plasma concentration was due to a decrease in UGT1A1 activity. Conversely, the order of values for CYP3A and CES activities was patient 3 > patient 1 > patient 2 and patient 2 > patient 1 > patient 3, respectively. Patient 3 had the lowest AUC of SN-38, caused by a lower level of CES activity and increased CYP3A activity. In this study, we indicated that the plasma AUC of SN-38 and AUC ratio of SN-38G/SN-38 may depend on changes in the activities of CYP3A, CES, and UGT1A1. Using pharmacokinetic analysis, it is possible to directly evaluate enzyme activity and consider what kind of enzyme variation causes the increase in the AUC of SN-38.

Abstract PD13-05: Delivery and activity of SN-38 by sacituzumab govitecan in breast cancer brain metastases

Abstract BACKGROUND: Sacituzumab Govitecan (SG, TRODELVY™) is an FDA approved antibody drug conjugate for treatment of metastatic triple negative breast cancer (TNBC). SG has payload and linker characteristics preferable for CNS delivery including a pH hydrolysable, a payload (SN-38) that is the active 1000-fold more potent than the parent compound CPT-11 and crosses the blood brain barrier. Our preliminary data showed SG activity in intracranial xenografts leading to our hypothesis that SG would achieve concentration of SN-38 within the breast cancer brain metastases (BCBM) that would be therapeutically relevant. METHODS: We undertook a single center, prospective, window of opportunity trial (NCT03995706) to examine the concentrations of SG, SN-38, and SN-38G in tumors patients undergoing craniotomy for BCBM (n=20) or recurrent glioblastoma (rGBM, n=10). A single dose of SG was administered at 10mg/kg IV the day prior to craniotomy. Tumor was collected and [SN-38] was analyzed via mass spectrometry (UHPLC-HRMS). following recovery patients resumed SG at 10mg/kg IV days 1 and 8 of 21 day cycle and were assessed for response or progression every third cycle by MRI. RESULTS: To date 21 patients have been treated, including 11 BCBM and 10 rGBM. UHPLC-HRMS analysis was performed in the first 10 tumors (n=4 and 6 respectively). For BCBM, total concentration of SN-38 varied from 173nM to 1160nM, with a mean concentration of 626nM. All GBM patients had residual measurable disease and 4 breast patients had measurable disease. With a median follow-up of 12 weeks from the first postoperative cycle in the first 14 patients, 2 partial responses from each group were observed (ORR of 28% and 50% at 12 weeks respectively). Updated results will be presented. CONCLUSIONS: SG achieves therapeutically relevant concentrations of SN-38 at 150-fold mean IC50s for BCBM. Early intracranial responses are encouraging and merit further evaluation. A multi-center trial of SG for HER2 negative BCBM (SWOG S2007) will be enrolling soon. Citation Format: Andrew J Brenner, Renu Pandey, Jennifer Chiou, John Floyd, Prathiba Surapreneni, Virginia Kaklamani, Kate Lathrop, Richard Crownover, Stefano Tiziani. Delivery and activity of SN-38 by sacituzumab govitecan in breast cancer brain metastases [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD13-05.

CPT11 with P-glycoprotein/CYP 3A4 dual-function inhibitor by self-nanoemulsifying nanoemulsion combined with gastroretentive technology to enhance the oral bioavailability and therapeutic efficacy against pancreatic adenocarcinomas

Therapeutic efficacies of orally administrated hydrophobic chemodrugs are decreased by poor water solubilities and reduced oral bioavailabilities by P-glycoprotein (P-gp) and CYP450. In this study, CPT11 alone or combined with dual-function inhibitors (baicalein (BA) silymarin (SM), glycyrrhizic acid (GA), and glycyrrhetinic acid (GLA)) of P-gp and CYP450 loaded in a lecithin-based self-nanoemulsifying nanoemulsion preconcentrate (LBSNENP) to improve the solubility and inhibit the elimination by P-gp and CYP450. Results revealed that the LBSNENP composed of Capryol 90, lecithin/Tween 80/Cremophor EL, and propylene glycol at a weight ratio of 18:58:24 (designated PC90C10P0) was optimally selected. Encapsulating CPT11 with PEO-7000K in PC90C10P10/30 further enhanced the resultant hydrogel to be gastro-retainable and to release CPT11 in a sustained manner. Pharmacokinetic study of CPT11-loaded PC90C10P0 administered orally revealed an absolute bioavailability (FAB, vs. intravenous CPT11) of 7.8 ± 1.01% and a relative bioavailability (FRB1, vs. oral solution of CPT11) of 70.7 ± 8.6% with a longer half-life (T 1/2) and mean residence time (MRT). Among the dual-function inhibitors, SM was shown to be the most influential in increasing the oral bioavailability of CPT11. SM also increased the plasma concentration of the SN-38 active metabolite, which formed from the enhanced plasma concentration of CPT11. It is concluded that treatment with CPT11 loaded in PC90C10P0 with or without solubilization with SM could expose tumors to higher plasma concentrations of both CPT11 and SN-38 leading to enhancement of tumor growth inhibition with no signs of adverse effects.

Effects of Protein and Calorie Restriction on the Metabolism and Toxicity Profile of Irinotecan in Cancer Patients.

Preclinical data suggests that protein and calorie restriction (PCR) might improve treatment tolerability without impairing antitumor efficacy. Therefore, we have studied the influence of PCR on irinotecan pharmacokinetics and toxicity. In this crossover trial, patients with liver metastases of solid tumors were included and randomized to treatment with irinotecan preceded by 5days of PCR (~30% caloric and ~70% protein restriction) during the first cycle and a second cycle preceded by a normal diet or vice versa. Pharmacokinetic blood sampling and biopsies of both healthy liver and liver metastases were performed. The primary end point was the relative difference in geometric means for the active metabolite SN-38 concentration in healthy liver analyzed by a linear mixed model. No significant differences were seen in irinotecan (+16.8%, P=0.22) and SN-38 (+9.8%, P=0.48) concentrations between PCR and normal diet in healthy liver, as well as in liver metastases (irinotecan: -38.8%, P=0.05 and SN-38: -13.8%, P=0.50). PCR increased irinotecan plasma area under the curve from zero to 24 hours (AUC0-24h ) with 7.1% (P=0.04) compared with normal diet, whereas the SN-38 plasma AUC0-24h increased with 50.3% (P<0.001). Grade ≥3 toxicity was not increased during PCR vs. normal diet (P=0.69). No difference was seen in neutropenia grade ≥3 (47% vs. 32% P=0.38), diarrhea grade ≥3 (5% vs. 21% P=0.25), and febrile neutropenia (5% vs. 16% P=0.50) during PCR vs. normal diet. In conclusion, plasma SN-38 exposure increased dramatically after PCR, whereas toxicity did not change. PCR did not alter the irinotecan and SN-38 exposure in healthy liver and liver metastases. PCR might therefore potentially improve the therapeutic window in patients treated with irinotecan.

CTNI-07. DELIVERY AND ACTIVITY OF SN-38 BY SACITUZUMAB GOVITECAN IN CNS TUMORS

Abstract BACKGROUND Sacituzumab Govitecan (SG, TRODELVY™) is an antibody drug conjugate, with payload and linker characteristics preferable for CNS delivery. SG utilizes a pH hydrolysable linker, allowing SN-38 to be released at the tumor site. SN-38 is the active component of Irinotecan and 1000-fold more potent than the parent compound. We observed SG activity in intracranial xenografts and hypothesized that SG would achieve therapeutically relevant concentration of SN-38 within the CNS. METHODS We performed a prospective, single center, window of opportunity trial (NCT03995706) to examine the intra-tumoral concentrations of SG, SN-38, and SN-38G in patients undergoing craniotomy for breast cancer brain metastases (BCBM, n=10) or recurrent glioblastoma (rGBM, n=10). Patients received a single dose of SG at 10mg/kg IV the day prior to craniotomy and tumor collected. [SN-38] was analyzed via mass spectrometry (UHPLC-HRMS). Patients resumed SG 10mg/kg IV days 1 and 8 of 21 day cycle following recovery and were assessed every third cycle by MRI using RANO criteria. RESULTS To date 16 patients have been treated, including 8 BCBM and 8 rGBM. UHPLC-HRMS analysis was performed in the first 10 tumors (n=4 and 6 respectively). For the rGBM patients, total concentration of SN-38 varied from 93nM to 680nM, with a mean concentration of 420nM. For BCBM, total concentration of SN-38 varied from 173nM to 1160nM, with a mean concentration of 626nM. All GBM patients had residual measurable disease and 4 breast patients had measurable disease. With a median follow-up of 12 weeks from the first postoperative cycle in the first 14 patients, 2 partial responses from each group were observed (ORR of 28% and 50% at 12 weeks respectively). CONCLUSIONS SG achieves therapeutically relevant concentrations of SN-38 at 40-fold mean IC50s for GBM, and 150-fold mean IC50s for BCBM. Early intracranial responses are encouraging and merit further evaluation.

373MO Delivery and activity of SN-38 by sacituzumab govitecan in CNS tumours

Sacituzumab Govitecan (SG, TRODELVY™) is unique as an antibody drug conjugate, with payload and linker characteristics preferable for CNS delivery. SG utilizes a pH hydrolysable linker, allowing SN-38 to be released at the tumor site, making the drug accessible to surrounding tumor cells. The payload, SN-38, is a topoisomerase inhibitor which crosses the blood-brain barrier and is a drug partner in CNS regimens. We have observed SG activity in intracranial xenograft models. We therefore hypothesized that SG would achieve therapeutically relevant concentration of SN-38 within the CNS.

Abstract CT156: Characterization of PEN-866, a Heat Shock Protein 90 (HSP90) binding conjugate of SN-38, in patient plasma and tumors from the first in human study

Abstract Background: Heat Shock Protein 90 (HSP90) is a molecular chaperone that aids in folding and trafficking of proteins and is upregulated in cells under stress. HSP90 is overexpressed in cancer cells and exists in the activated configuration within the tumor microenvironment. PEN-866 is a novel small molecule drug conjugate containing a HSP90 targeting moiety that accumulates in tumors and releases its payload SN-38 through a cleavable linker within the tumor cells. The first in human phase 1/2a PEN-866 study was designed to assess safety, pharmacokinetics (PK), and exploratory biomarkers of PEN-866 related to its mechanism of action. Here we describe the evaluation of PEN-866 and the payload SN-38 in plasma and tumors. Methods: Patients with advanced solid malignancies were enrolled in dose escalation cohorts and received PEN-866 IV on days 1, 8, and 15 in 28-days cycles, over a dose range of 16-228 mg/m2. Plasma samples were collected up to 8 days after the first dose and up to 24 hours after the third dose. Non-compartmental analysis was performed to obtain PK parameters. Optional tumor biopsies were collected from two patients and analyzed for PEN-866 and SN-38 concentrations. Results: PEN-866 plasma concentration profile was biphasic with a rapid concentration decline after end of infusion resulting in an average half-life (t½) of approximately 10 hours across all dose cohorts. PEN-866 maximum plasma concentrations (Cmax) ranged from 0.69 to 54 µg/mL and area under the concentration curve (AUC) from 0.80 to 88 h·µg/mL. The Cmax and AUC increased higher than dose proportionally at the lower dose levels which resulted in higher clearance (CL) and volume of distribution (Vd) variability. Free SN-38 AUC's were generally low demonstrating linker stability in circulation and low systemic exposure. PEN-866 and SN-38 levels in patient tumors confirmed accumulation and retention of the conjugate up to 6 days after PEN-866 dose and the targeted release of SN-38. Conclusion: PEN-866 has an extended plasma half-life in patients with advanced solid malignancies and showed good stability in circulation with limited plasma exposure of the payload SN-38. Analysis of tumor biopsies up to 6 days after dosing demonstrated significant accumulation and extended exposures of PEN-866 and SN-38 within the tumor tissue that exceed plasma exposures. Citation Format: Anish Thomas, Kristina Kriksciukaite, Gerald Falchook, Johanna Bendel, Susanna Ulahannan, Christophe Redon, Laura Mei, Kerry Whalen, Jeffrey Bloss, Mark T. Bilodeau. Characterization of PEN-866, a Heat Shock Protein 90 (HSP90) binding conjugate of SN-38, in patient plasma and tumors from the first in human study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT156.

Abstract 3068: The glycoprotein inhibitors overcome the resistance of the topoisomerase inhibitors in small cell lung cancer

Abstract Small cell lung cancer (SCLC) is a highly aggressive disease with median survival of &amp;lt;2 years. Most patients respond initially to the topoisomerase inhibitors, resistance rapidly emerges. The purpose is overcoming the resistance of the topoisomerase inhibitors in SCLCs. To identify the key factors for the resistance of the topoisomerase I (SN38) or II (VP-16) inhibitors in SCLCs, we analyzed MTS cell proliferation assay. We identified 8 sensitive cell lines and 2 resistant cell lines. We established 4 resistant cell lines by continuous exposure to increasing concentrations of SN-38 or VP-16 stepwise. RNA sequencing was performed using the established cell lines to discover novel therapeutic targets associated with the resistance to topoisomerase inhibitors. We found that whenever the drug efflux protein ATP-binding cassette transporter B1 (ABCB1) was associated the with resistance of VP-16, ATP-binding cassette super-family G member 2 (ABCG2) was associated with the resistance of SN-38. The silencing of ABCG2 or ABCB1 in every resistant cell line, could induce synergistic apoptosis of every cell line. Elacridar and tariquidar which are glycoprotein inhibitors, recovered the sensitivity of SN38 or VP-16 in every resistant line, increased expression of signaling proteins associated with DNA damage and cell-cycle checkpoints, and promoted G2/M arrest and apoptosis. Furthermore, we are going to analyze the expressions of ABCG2 and ABCB1 in serum before and after the treatment of VP-16 or CPT-11. These results suggested the glycoprotein inhibitors, which phase I study is ongoing, could be a promising therapeutic strategy for the purpose of preventing the resistance of topoisomerase inhibitors in SCLCs. Citation Format: Rintaro Noro, Miwako Omori, Aya Fukuizumi, kuniko Matsuda, Mariko Hirao, Satoshi Takahashi, Natsuki Takano, Shinji Nakamichi, Teppei Sugano, Akihiko Miyanaga, Yuji Minegishi, Masahiro Seike, Kaoru Kubota, Akihiko Gemma. The glycoprotein inhibitors overcome the resistance of the topoisomerase inhibitors in small cell lung cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3068.

A PK/PD mathematical model to forecast severe toxicities in pancreatic cancer patients treated with FOLFIRINOX regimen.

e16774 Background: FOLFIRINOX regimen is the most efficient treatment in pancreatic adenocarcinoma. However, this triple-therapy causes significant and dose-limiting toxic effects leading to empirical dose-reduction, postponement of the forthcoming courses and sometimes treatment discontinuation. Dose-limiting toxicities with FOLFIRINOX are mostly oxaliplatin-induced peripheral neuropathy (OIPN) and irinotecan-induced diarrhoea (IID). The first aim of our study was to establish dose-concentration-toxicity relationships for these two main ordinal toxicities. Second, we aimed to perform in silico simulations to define the optimal FOLFIRINOX administration protocol (i.e., dosing, scheduling, sequencing) for a maximal benefit to risk ratio. Methods: We performed a retrospective pharmacometric analysis from clinical data collected in three French institutes. Patients had all confirmed diagnosis of PDAC treated with FOLFIRINOX as first line regimen. Demographic characteristics, toxicity data and dosage modifications were collected. Two mathematical models connecting dose – concentration – toxicity (PKPD Tox model) were developed using Monolix2019 to describe both OIPN and IID. Results: Data from 75 patients (36 females/39 males) treated with FOLFIRINOX regimen between 2015-2018 and representing 566 courses were collected. Median age was 65.4 years (range 29-78). The performance status at the start of treatment was 0-1 for 70% of patients. The most frequent location of the tumor was pancreatic head (50%). 91% of patients were subject to empirical dose reduction during their treatment. Oxaliplatin doses were decreased in 258 courses and stopped in 66 courses. Irinotecan doses were decreased in 257 courses and stopped in 33 courses. Overall, 130 IID and 198 OIPN events were observed. From these data, two different PKPD Tox models were developed. The individual concentrations of SN38 (active metabolite of irinotecan) and oxaliplatin were simulated with population PK models, either home-built or taken from the literature. Concentrations were translated into adequate exposure via an interface model developed by our group. Exposure was finally related to a pharmacodynamic model to predict probabilities assigned to each grade of IID or OIPN. Conclusions: These PKPD Tox models help to predict dose-limiting toxicities upon FOLFIRINOX and are useful to select the administration protocol of FOLFIRINOX minimizing the occurrence probabilities of treatment-related neuropathy and diarrhoea, while maintaining efficacy.

Targeted MMP-2 responsive chimeric polymersomes for therapy against colorectal cancer

In the current study, polyethylene glycol (PEG) was linked to polylactide (PLA) through the synthetic peptide PVGLIG which can be selectively cleaved by the tumor-associated matrix metalloproteinase 2 (MMP-2) enzyme.The synthesized chimeric triblock polymer of PEG-b-PVGLIG-PLA was implemented to form nanoscale self-assemble chimeric polymersomes.The hydrophobic SN38 was loaded into polymersomes with 70.3% ± 3.0% encapsulation efficiency demonstrating monodispersed spherical morphologies with 172 ± 30 nm dimension.The prepared chimeric polymersomal formulation provided controlled release of SN38 at physiological condition while illustrating seven-folds higher release rate when exposed to MMP-2 enzyme.At the next stage, AS1411 aptamer was conjugated onto the surface of MMP-2 responsive polymersomal formulation in order to provide guided drug delivery against nucleolin positive cells. In vitro cellular toxicity assay against C26 cell line (nucleolin positive) demonstrated significantly higher toxicity of targeted formulation in comparison with non-targeted one in low SN38 concentrations (0.15–1.25 μg/mL).In vivo study in mice bearing subcutaneous C26 tumor showed higher therapeutic index for MMP-2 responsive chimeric polymersomal formulation of SN38 in comparison with non-responsive one. On the other hand, AS1411 aptamer-targeted MMP-2 responsive chimeric polymersomal formulation exhibited highest therapeutic index compared to other groups.It could be concluded that the targeted chimeric polymersomes bearing both cleavable peptide sequence between their blocks and targeting ligand on their surface, provide favorable characteristics as an ideal delivery system against cancer.

Irinotecan-mediated diarrhea is mainly correlated with intestinal exposure to SN-38: Critical role of gut Ugt

Background and purposeIrinotecan-induced diarrhea (IID) results from intestinal damages by its active metabolite SN-38. Alleviation of these damages has focused on lowering luminal SN-38 concentrations. However, it is unclear if the enteric bioavailability of SN-38 is mostly dependent on luminal SN-38 concentrations. Experimental approachIrinotecan (50 mg/kg, i.p. once daily for 6 days) was administered to female wildtype FVB, Mdr1a (−/−), Mrp2 (−/−) and Bcrp1 (−/−) mice for pharmacokinetic (PK), toxicokinetic (TK) and biodistribution studies. Plasma PK/TK profiles and tissues drug distribution were determined after first or sixth daily doses, along with activities of blood and gut esterases and intestinal Ugts. Caco-2 cells and bile-cannulate mice were used to further investigate intestinal and biliary disposition of irinotecan and its metabolites. Key resultsSignificant differences in IID severity were observed with the susceptible rank of Bcrp1(−/−) > wildtype FVB > Mdr1a(−/−) > Mrp2(−/−). This rank order did not correlate with biliary excretion rates of SN-38/SN-38G. Rather, the severity was best correlated (R = 0.805) with the intestinal ratio of Css SN-38/SN-38G, a measure of gut Ugt activity. On the contrary, IID was poorly correlated with plasma AUC ratio of SN-38/SN-38G (R = 0.227). Increased intestinal esterase activities due to repeated dosing and gut efflux transporter functionality are the other key factors that determine SN-38 enteric exposures. Conclusion and implicationsIntestinal SN-38 exposure is mainly affected by intestinal Ugt activities and blood esterase activities, and strongly correlated with severity of IID. Modulating intestinal SN-38 concentration and gut Ugt expression should be the focus of future studies to alleviate IID.

Antagonistic Effects of CAPE (a Component of Propolis) on the Cytotoxicity and Genotoxicity of Irinotecan and SN38 in Human Gastrointestinal Cancer Cells In Vitro.

The incidence of gastrointestinal cancers is increasing every year. Irinotecan (CPT-11), a drug used in the treatment of colorectal cancer and gastric cancer, is metabolized by carboxylesterases to an active metabolite, SN-38, which is more cytotoxic. CAPE (caffeic acid phenethyl ester) is an active component of propolis, which has a high antibacterial, antiviral, and antineoplastic potential. This study analyses the impact of CAPE on the cytotoxic (MTT assay), genotoxic (comet assay) and proapoptotic (caspase-3/7 activity) potential of irinotecan and its metabolite SN-38 in cultures of gastrointestinal neoplastic cells (HCT116, HT29, AGS). Cytotoxicity and genotoxicity activities of these compounds were carried out in comparison with human peripheral blood lymphocytes (PBLs) in vitro. The antioxidant potential of CAPE was investigated in relation H2O2-induced oxidative stress in the both neoplastic cells and PBLs. CAPE expressed cytotoxic, genotoxic, and pro-apoptotic activity against AGS, HCT116, and HT29 tumor cells. CAPE, in the presence of different concentrations of irinotecan or SN38, decreased the cytotoxicity, genotoxicity, and pro-apoptotic activity in these cell lines, but it has no such action on normal human peripheral blood lymphocytes.

Regulation of breast cancer resistance protein and P-glycoprotein by ezrin, radixin and moesin in lung, intestinal and renal cancer cell lines.

Ezrin (Ezr), radixin (Rdx) and moesin (Msn) (ERM) proteins anchor other proteins to the cell membrane, serving to regulate their localization and function. Here, we examined whether ERM proteins functionally regulate breast cancer resistance protein (BCRP) and P-glycoprotein in cell lines derived from lung, intestinal and renal cancers. ERM proteins were each silenced with appropriate siRNA. BCRP and P-gp functions were evaluated by means of efflux and uptake assays using 7-ethyl-10-hydroxycamptothecin (SN-38) and rhodamine123 (Rho123) as specific substrates, respectively, in non-small cell lung cancer HCC827 cells, intestinal cancer Caco-2 cells and renal cancer Caki-1 cells. In HCC827 cells, the efflux rates of SN-38 and Rho123 were significantly decreased by knockdown of Ezr or Msn, but not Rdx. However, BCRP function was unaffected by Ezr or Rdx knockdown in Caco-2 cells, which do not express Msn. In Caki-1 cells, Rdx knockdown increased the intracellular SN-38 concentration, while knockdown of Ezr or Msn had no effect. Our findings indicate that regulation of BCRP and P-gp functions by ERM proteins is organ-specific. Thus, if the appropriate ERM protein(s) are functionally suppressed, accumulation of BCRP or P-gp substrates in lung, intestine or kidney cancer tissue might be specifically increased.

Effects of inflammation on irinotecan pharmacokinetics and development of a best-fit PK model

Irinotecan is a chemotherapeutic drug used in the treatment of advanced colorectal cancer and elevated blood concentrations of its active metabolite, SN-38 leads to increased gastrointestinal (GI) toxicity and diarrhea in patients. In this study, we investigated the effects of inflammation on the pharmacokinetics (PK) of irinotecan (CPT-11) and its active metabolite, SN-38. Mice were i.p.-injected with either saline or lipopolysaccharide (LPS) to induce inflammation. After 16 h, irinotecan was administered orally. Blood was collected from the tail vein of mice from 0 to 24 h after dosing. Concentrations of irinotecan, SN-38 and SN-38G were analyzed using LC-MS/MS. The AUC, Cmax, and tmax were derived using WinNonlin® 5.2. A PK model was developed using Phoenix NLME® to describe the PK of irinotecan and SN-38 during inflammation. Results indicated a significant increase in the blood concentrations of irinotecan and SN-38 in mice during inflammation. The AUC of irinotecan and SN-38 in LPS group were 2.6 and 2-folds, respectively, of those in control saline-treated mice. The Cmax of irinotecan and SN-38 in LPS treated mice were 2.4 and 2.3-folds of those in saline-treated mice. The PK model was successfully developed and validated. The best-fit plots of individual PK analysis showed a good correlation between observed and predicted concentrations of irinotecan and SN-38. Together, this study reveals that SN-38 concentrations are elevated during inflammation, which may increase the GI toxicity and diarrhea in patients who receive irinotecan; and the developed PK model can quantitatively describe the PK of irinotecan and SN-38 during inflammation.

1913P - Effects of dietary restriction in cancer patients receiving irinotecan

BackgroundIrinotecan is widely used, but also known for its severe toxicities neutropenia and diarrhea. Based on preclinical data, combined caloric and protein restriction (CCPR) might improve treatment tolerability without impairing antitumor effect. Therefore, we studied the influence of CCPR on irinotecan pharmacokinetics and toxicity. MethodsIn this cross-over trial, patients with liver metastases of solid tumors were included and randomized to treatment with irinotecan preceded by 5 days of CCPR (∼30% caloric and ∼70% protein restriction) during the 1st cycle and a 2nd cycle preceded by a normal diet (ND) or vice versa. During both cycles, 24-hours blood sampling was performed and 24-26hours after infusion biopsies of both healthy liver (HL) and liver metastasis (LM) were taken. Primary endpoint was the relative difference in geometric means for the active metabolite SN-38 concentration in HL, as analyzed by a linear mixed model. Secondary endpoints included irinotecan and SN-38 concentrations in LM, plasma area under the curve (AUC0-24h), and toxicity. ResultsInterpatient variability (n=19) in tissue irinotecan and SN-38 concentrations was high, showing no significant differences in irinotecan (+16.8%, 95% CI: -9.7-51.1%, P=0.227) and SN-38 (+9.8%, 95% CI: -16.4-44.2%, P=0.48) concentrations between CCPR and ND in HL, as well as in LM (irinotecan: -38.8%, 90% CI: -59.3:-7.9%, P=0.05 and SN-38: -13.8%, 90% CI:-40.7-25.4%, P=0.50). CCPR increased irinotecan plasma AUC0-24h with 7.1% (95% CI: 0.3-14.5%, P=0.04) compared to ND, while the SN-38 plasma AUC0-24h increased with 50.3% (95% CI: 34.6-67.9%, P<0.001). CCPR was well tolerated with low incidence of grade ≥3 therapy related toxicity. Grade ≥3 toxicity was not increased during CCPR vs ND (P=0.69). No difference was seen in neutropenia grade ≥3 (47% vs 32% P=0.38), diarrhea grade ≥3 (5% vs 21% P=0.25), febrile neutropenia (5% vs 16% P=0.50) and hospitalization (11% vs 21% P=0.634) during CCPR vs ND. ConclusionsCCPR resulted in a dramatically increased plasma SN-38 exposure, while toxicity did not change. CCPR did not result in altered irinotecan and SN-38 exposure in HL and LM. CCPR might therefore potentially improve the therapeutic window in patients treated with irinotecan. Clinical trial identificationNetherlands Trial Register NL5624 (NTR5731) release date: 2016-03-04. Legal entity responsible for the studyA.H.J. Mathijssen. FundingHas not received any funding. DisclosureS.L. Koolen: Speaker Bureau / Expert testimony: Novartis; Speaker Bureau / Expert testimony: Roche; Speaker Bureau / Expert testimony: Pfizer; Research grant / Funding (institution): Astellas; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Cristal Therapeutics; Travel / Accommodation / Expenses: Ipsen. R.H.J. Mathijssen: Research grant / Funding (institution): Astellas; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): Boehringer; Research grant / Funding (institution): Cristal Therapeutics; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Pamgene; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Roche; Research grant / Funding (institution): Sanofi; Honoraria (institution): Servier; Honoraria (institution): Novartis; Travel / Accommodation / Expenses: Pfizer; Travel / Accommodation / Expenses: Astellas. All other authors have declared no conflicts of interest.

437TiP - CNS penetration and preliminary efficacy of sacutizumab govitecan in breast brain metastasis and glioblastoma: A surgical study

BackgroundSacituzumab govitecan (SG) is an antibody drug conjugate (ADC) that targets Trop-2 for the selective delivery of SN-38 to tumors. SG carries SN-38, a topoisomerase inhibitor active in the nanomolar range for most cells (including TNBC and GBM) and freely cross the blood brain barrier. SN-38 is conjugated to SG by a linker designated CL2A which is sensitive to acidic and conditions. SG was evaluated in a single-arm, multicenter trial with relapsed/refractory metastatic triple negative breast cancer (TNBC) with impressive results including a confirmed objective response rate of 30%, with responses occurring early (median onset of 1.9 months) and being durable (median duration 8.9m). SG has since been granted priority review designation by the FDA, with approval anticipated. Brain metastases is a significant concern in this patient population, but whether this agent is able to target the CNS through the blood brain barrier is unknown. Based upon the characteristics of this specific ADC, including the use of a pH labile linker and a payload with good CNS penetration, it is our specific hypothesis that the SG can achieve intratumoral concentrations of SN-38 sufficient to achieve therapeutic benefit in patients with neoplastic involvement of the brain. We further hypothesize that while total concentration of SN-38 will correlate with expression of trop2, free SN-38 will correlate more strongly with intratumoral hypoxia. Trial designSingle center, non-randomized, prospective study of SG in subjects with CNS involvement and planned surgical resection. SG is given as single dose at 10mg/kg administered pre-operatively on Day-1. Surgery will be followed by post-operative treatment with sacituzumab govitecan given intravenously with standard dose of 10mg/kg on day1 and day 8 of 21-day cycle, until disease progression. Approximately 20 patients, 2 cohorts of 10 patients each with GBM and breast brain tumors from TNBC.Tumors will be analyszed for total antibody (hRS7 + hRS7-SN-38), free SN-38, and total SN-38 (free SN-38 + hRS7-SN-38) concentrations in tumor tissue. Correlations will be made to Trop2 expression and hypoxia. Legal entity responsible for the studyUniversity of Texas Health San Antonio. FundingMays Cancer Center, Kolitz Endowment. DisclosureA.J. Brenner: Research grant / Funding (institution): Immunomedics. V. Kaklamani: Research grant / Funding (institution): Immunomedics. V. Madhusudanan-Kunnuparampil: Research grant / Funding (institution): Immunomedics. All other authors have declared no conflicts of interest.

TRLS-08. CNS PENETRATION AND PRELIMINARY EFFICACY OF SACUTIZUMAB GOVITECAN IN BREAST BRAIN METASTASIS AND GLIOBLASTOMA: A SURGICAL STUDY

Sacituzumab govitecan (SG) is an antibody drug conjugate (ADC) that targets Trop-2 for the selective delivery of SN-38 to tumors. SG carries SN-38, a topoisomerase inhibitor active in the nanomolar range for most cells (including TNBC and GBM) and freely cross the blood brain barrier. SN-38 is conjugated to SG by a linker designated CL2A which is sensitive to acidic conditions. SG has since been granted priority review designation by the FDA, with approval anticipated for triple negative breast cancer. Brain metastases is a significant concern in this patient population, but whether this agent is able to target the CNS through the blood brain barrier is unknown. Based upon the characteristics of this specific ADC, including the use of a pH labile linker and a payload with good CNS penetration, it is our specific hypothesis that the SG can achieve intratumoral concentrations of SN-38 sufficient to achieve therapeutic benefit in patients with neoplastic involvement of the brain. We further hypothesize that while total concentration of SN-38 will correlate with expression of trop2, free SN-38 will correlate more strongly with intratumoral hypoxia. To address this, we are performing a non-randomized, prospective study of SG in subjects with CNS involvement and planned surgical resection. SG is given as single dose at 10mg/kg pre-operatively on Day-1. Surgery will be followed by post-operative treatment with sacituzumab govitecan given intravenously with standard dose of 10 mg/kg on day1 and day 8 of 21-day cycle, until disease progression. Approximately 20 patients, 2 cohorts of 10 patients each with GBM and breast brain tumors, will be enrolled. Tumors will be analyzed for total antibody, free SN-38, and total SN-38 (free SN-38 + Antibody-SN38) concentrations in tumor tissue. Correlations will be made to Trop2 expression and hypoxia. Interim results will be presented.

Xiao-Chai-Hu-Tang (XCHT) Intervening Irinotecan's Disposition: The Potential of XCHT in Alleviating Irinotecan-Induced Diarrhea.

Diarrhea is a severe side effect of irinotecan, a pro-drug of SN-38 used for the treatment of many types of cancers. Pre-clinical and clinical studies showed that decreasing the colonic exposure of SN-38 can mitigate irinotecan-induced diarrhea. The purpose of this study is to evaluate the anti-diarrhea potential of Xiao-Chai-Hu-Tang (XCHT), a traditional Chinese herbal formula, against irinotecan-induced diarrhea by determining if and how XCHT alters the disposition of SN-38. LC-MS/MS was used to quantify the concentrations of irinotecan and its major metabolites (i.e., SN-38, SN-38G). An Intestinal perfusion model was used to determine the effect of XCHT on the biliary and intestinal secretions of irinotecan, SN-38, and SN-38G. Pharmacokinetic (PK) studies were performed to determine the impact of XCHT on the blood and fecal concentrations of irinotecan, SN-38, and SN-38G. The results showed that XCHT significantly inhibits both biliary and intestinal excretions of irinotecan, SN-38, and SN-38G (range: 35% to 95%). PK studies revealed that the fecal concentrations of irinotecan and SN-38 were significantly decreased from 818.35 ± 120.2 to 411.74 ± 138.83 µg/g or from 423.95 ± 76.44 to 245.63 ± 56.72 µg/g (p<0.05) by XCHT, respectively, suggesting the colonic exposure of SN-38 is significantly decreased by XCHT. PK studies also showed that the plasma concentrations of irinotecan, SN-38, and SN-38G were not affected by XCHT. In conclusion, XCHT significantly decreased the exposure of SN-38 in the gut without affecting its plasma level, thereby possessing the potential of alleviating irinotecan-induced diarrhea without negatively impacting its therapeutic efficacy.

Selective TACE with irinotecan-loaded 40 \u03bcm microspheres and FOLFIRI for colorectal liver metastases: phase I dose escalation pharmacokinetic study

BackgroundEfficacy of treatments for colorectal liver metastases after failure of first-line chemotherapy is limited. The aim of this study was to prospectively evaluate the feasibility, tolerability, and pharmacokinetics of selective transarterial chemoembolization (TACE) with irinotecan-loaded 40 μm microspheres combined with systemic FOLFIRI for colorectal liver metastases refractory to oxaliplatin regimen.MethodsThe dose escalation study was conducted in three patient groups with different amounts of irinotecan loaded (50, 75 and 100 mg per mL-microspheres). Selective catheterization was performed to embolize subsegments or segments of located tumors using TACE navigation system. FOLFIRI was administrated 7 days after TACE. Plasma concentration was measured before and time points after administration.ResultsNine patients successfully underwent a total of 22 TACE procedures. Dose-limiting toxicity did not appear at any level. The overall response rate was 55.6%. The median progression free and overall survival were 8.1 and 18.2 months, respectively. The AUC and Cmax of plasma SN-38 per 1 mg injected irinotecan dose were significantly higher in irinotecan-loaded microspheres compared with FOLFIRI (P = 0.009 and P < 0.001, respectively).ConclusionSelective TACE using 40 μm irinotecan-loaded microspheres combined with systemic FOLFIRI was feasible and safe even when a high dose of irinotecan was loaded. Irinotecan-loaded microspheres resulted in a higher plasma concentration and AUC of SN-38 than treatment with FOLFIRI. Further large scale trials to evaluate the efficacy are mandatory.Trial registrationUniversity Hospital Medical Information Network (UMIN) Clinical Trials Registry, Registration number; UMIN000015367; Registered date; 08,10,2014.

Abstract 227: BPRDP056, a novel small molecule drug conjugate specifically targeting phosphatidylserine for cancer therapy

Abstract Zinc(II)-dipicolylamine (Zn-DPA) have been described to specifically complex with phosphatidylserine (PS), which has a higher level at the external surface of cancer cells in tumorigenic condition. BPRDP056 is a Zn-DPA-SN38 conjugate designed to provide a PS-targeting drug delivery of cytotoxic payload SN-38 at the tumor microenvironment, thereby, decrease the dosage of SN38, while induce apoptosis in cancer cells. The in vivo therapeutic efficacy of BPRDP056 against the growths of human tumors has been shown significant in mice subcutaneously bearing a tumor type of pancreas, prostate, colon, liver, breast and glioblastoma, as well as in mice with an orthotopic pancreatic tumor. BPRDP056 shrunk tumors at a lower dosing intensity (~20%) of SN38 compared to CPT-11 in all models tested. Micro-Western assays showed that BPRDP056 exhibited apoptotic cell death signal levels similar to those of CPT-11 in the treated tumors in mice. Furthermore, pharmacokinetic and preliminary toxicology studies showed that BPRDP056 has a good stability in circulation with an acceptable therapeutic safety window in mice. BPRDP056 has been demonstrated with a tumor targeting ability and thus increases the cytotoxic payload SN38 concentration in situ for improved efficacy. Its therapeutic spectrum against malignant neoplasm will be expected to cover the PS-rich tumor microenvironment of all cancer types. BPRDP056 is a first-in-class Small Molecule Drug Conjugate for anti-cancer therapy. Citation Format: Chia-Yu Hsu, Yun-Yu Chen, Chen-Fu Lo, Tai-Yu Chiu, Ching-Ping Chen, Chen-Lung Huang, Chung-Yu Huang, Min-Hsien Wang, Yu-Sheng Chao, Joe C. Shih, Teng-Kuang Yeh, Lun K. Tsou, Chiung-Tong Chen. BPRDP056, a novel small molecule drug conjugate specifically targeting phosphatidylserine for cancer therapy [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 227.