A Randomized Trial of Mesenchymal Stromal Cells for Moderate to Severe Acute Respiratory Distress Syndrome from COVID-19

Rationale: There are limited therapeutic options for patients with coronavirus disease (COVID-19)-related acute respiratory distress syndrome with inflammation-mediated lung injury. Mesenchymal stromal cells offer promise as immunomodulatory agents. Objectives: Evaluation of efficacy and safety of allogeneic mesenchymal cells in mechanically-ventilated patients with moderate or severe COVID-19-induced respiratory failure. Methods: Patients were randomized to two infusions of 2 million cells/kg or sham infusions, in addition to the standard of care. We hypothesized that cell therapy would be superior to sham control for the primary endpoint of 30-day mortality. The key secondary endpoint was ventilator-free survival within 60 days, accounting for deaths and withdrawals in a ranked analysis. Measurements and Main Results: At the third interim analysis, the data and safety monitoring board recommended that the trial halt enrollment as the prespecified mortality reduction from 40% to 23% was unlikely to be achieved (n = 222 out of planned 300). Thirty-day mortality was 37.5% (42/112) in cell recipients versus 42.7% (47/110) in control patients (relative risk [RR], 0.88; 95% confidence interval, 0.64-1.21; P = 0.43). There were no significant differences in days alive off ventilation within 60 days (median rank, 117.3 [interquartile range, 60.0-169.5] in cell patients and 102.0 [interquartile range, 54.0-162.5] in control subjects; higher is better). Resolution or improvement of acute respiratory distress syndrome at 30 days was observed in 51/104 (49.0%) cell recipients and 46/106 (43.4%) control patients (odds ratio, 1.36; 95% confidence interval, 0.57-3.21). There were no infusion-related toxicities and overall serious adverse events over 30 days were similar. Conclusions: Mesenchymal cells, while safe, did not improve 30-day survival or 60-day ventilator-free days in patients with moderate and/or severe COVID-19-related acute respiratory distress syndrome.

Efficacy and Safety of Ensovibep for Adults Hospitalized With COVID-19 : A Randomized Controlled Trial

BACKGROUND

Ensovibep (MP0420) is a designed ankyrin repeat protein, a novel class of engineered proteins, under investigation as a treatment of SARS-CoV-2 infection.

OBJECTIVE

To investigate if ensovibep, in addition to remdesivir and other standard care, improves clinical outcomes among patients hospitalized with COVID-19 compared with standard care alone.

DESIGN

Double-blind, randomized, placebo-controlled, clinical trial. (ClinicalTrials.gov: NCT04501978).

SETTING

Multinational, multicenter trial.

PARTICIPANTS

Adults hospitalized with COVID-19.

INTERVENTION

Intravenous ensovibep, 600 mg, or placebo.

MEASUREMENTS

Ensovibep was assessed for early futility on the basis of pulmonary ordinal scores at day 5. The primary outcome was time to sustained recovery through day 90, defined as 14 consecutive days at home or place of usual residence after hospital discharge. A composite safety outcome that included death, serious adverse events, end-organ disease, and serious infections was assessed through day 90.

RESULTS

An independent data and safety monitoring board recommended that enrollment be halted for early futility after 485 patients were randomly assigned and received an infusion of ensovibep (n = 247) or placebo (n = 238). The odds ratio (OR) for a more favorable pulmonary outcome in the ensovibep (vs. placebo) group at day 5 was 0.93 (95% CI, 0.67 to 1.30; P = 0.68; OR > 1 would favor ensovibep). The 90-day cumulative incidence of sustained recovery was 82% for ensovibep and 80% for placebo (subhazard ratio [sHR], 1.06 [CI, 0.88 to 1.28]; sHR > 1 would favor ensovibep). The primary composite safety outcome at day 90 occurred in 78 ensovibep participants (32%) and 70 placebo participants (29%) (HR, 1.07 [CI, 0.77 to 1.47]; HR < 1 would favor ensovibep).

LIMITATION

The trial was prematurely stopped because of futility, limiting power for the primary outcome.

CONCLUSION

Compared with placebo, ensovibep did not improve clinical outcomes for hospitalized participants with COVID-19 receiving standard care, including remdesivir; no safety concerns were identified.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Pilot-scale production of expansile nanoparticles: Practical methods for clinical scale-up

One of the foremost challenges in translating nanoparticle technologies to the clinic is the requirement to produce materials on a large-scale. Scaling nanoparticle production methods is often non-trivial, and the success of these endeavors is frequently governed by whether or not an intermediate level of production, i.e., "pilot-scale" production, can be achieved. Pilot-scale production at the one-liter scale serves as a proof-of-concept that large-scale production will be possible. Here, we describe the pilot-scale production of the expansile nanoparticle (eNP) technology including verification of activity and efficacy following scaleup. We describe the challenges of sonication-based emulsification procedures and how these were overcome by use of a Microfluidizer technology. We also describe the problem-solving process that led to pre-polymerization of the nanoparticle polymer-a fundamental change from the lab-scale and previously published methods. Furthermore, we demonstrate good control over particle diameter, polydispersity and drug loading and the ability to sterilize the particles via filtration using this method. To facilitate long-term storage of these larger quantities of particles, we investigated six lyoprotectants and determined that sucrose is the most compatible with the current system. Lastly, we demonstrate that these changes to the manufacturing method do not adversely affect the swelling functionality of the particles, their highly specific localization to tumors, their non-toxicity in vivo or their efficacy in treating established intraperitoneal mesothelioma xenografts.

Small bowel and abdominal wall transplantation: A novel technique for synchronous revascularization

Abdominal wall transplantation (AWT) was introduced in 1999 in the context of reconstruction of complex abdominal wall defects in conjunction with visceral organ transplantation. As of recently, 38 cases of total AWT have been performed worldwide, about half of which were performed in the United States. While AWT is technically feasible, one of the major challenges presenting to the reconstructive surgeon is time to revascularization of the donor abdominal wall (AW), given the immediate proximity of the visceral organ and AWT. The authors report a novel AW revascularization technique during a synchronous small bowel and AWT in a 37-year-old man.

Perspectives on Inflammatory Breast Cancer (IBC) Research, Clinical Management and Community Engagement from the Duke IBC Consortium

Inflammatory breast cancer (IBC) is an understudied and aggressive form of breast cancer with a poor prognosis, accounting for 2-6% of new breast cancer diagnoses but 10% of all breast cancer-related deaths in the United States. Currently there are no therapeutic regimens developed specifically for IBC, and it is critical to recognize that all aspects of treating IBC - including staging, diagnosis, and therapy - are vastly different than other breast cancers. In December 2014, under the umbrella of an interdisciplinary initiative supported by the Duke School of Medicine, researchers, clinicians, research administrators, and patient advocates formed the Duke Consortium for IBC to address the needs of patients in North Carolina (an ethnically and economically diverse state with 100 counties) and across the Southeastern United States. The primary goal of this group is to translate research into action and improve both awareness and patient care through collaborations with local, national and international IBC programs. The consortium held its inaugural meeting on Feb 28, 2018, which also marked Rare Disease Day and convened national research experts, clinicians, patients, advocates, government representatives, foundation leaders, staff, and trainees. The meeting focused on new developments and challenges in the clinical management of IBC, research challenges and opportunities, and an interactive session to garner input from patients, advocates, and community partners that would inform a strategic plan toward continuing improvements in IBC patient care, research, and education.

Abstract LB-95: Estrogen receptor mRNA-directed therapy for triple-negative breast cancer

Introduction: A significant number of histologically triple negative breast cancer (TNBC) cells express substantial estrogen receptor (ER) mRNA but do not express ER protein as a result of rapid proteolytic degradation. Here we assessed whether proteasome inhibitors could sensitize such cells to tamoxifen-induced growth suppression. Methods: Data from the Katzenellenbogen laboratory elegantly demonstrate that in high ER mRNA MDA-MB-468 cells, ER protein is rapidly degraded via proteosomal degradation (Bhatt et al. MCB, 2012).Utilizing established human TNBC cell lines that express high ER mRNA (BT-20, MDA-MB-468, and newly established human TNBC cell lines from our laboratory MCJB2 and MCJB11), we defined a therapeutic strategy using the proteasome inhibitor carfilzomib in combination with the antiestrogen tamoxifen that demonstrates antitumor synergy. Results: We found that administration of carfilzomib in TNBC cell lines with high ER mRNA restored ER protein expression, and that combining this treatment with tamoxifen treatment led to enhanced growth suppression. We found that the TNBC MDA-MB-231 cells, which express no ER mRNA, show some growth suppression, but that tamoxifen provided no further growth suppression with these cells. We have previously shown that combined epigenetic therapy [methyltransferase inhibitor (decitabine) plus a histone deacetylase inhibitor (HDACi; romidepsin)] provided antitumor synergy in MDA-MB-231 cells via upregulation of the soluble Wnt suppressor, secreted frizzled protein 1 (sFRP1; Cooper et al. CCR, 2012). In addition, we show that this epigenetic therapy restores silenced ER mRNA and protein levels in MDA-MB-231 cells, and that combination of this epigenetic therapy with tamoxifen in MDA-MB-231 cells led to enhanced growth suppression by tamoxifen. We are currently testing these therapeutic strategies in vivo using established TNBC cell lines and our newly developed patient derived xenograft (PDX) mouse models that express either ERhigh or ERlow mRNA. Conclusions: If validated in animal models, we propose that ER mRNA expression level in TNBC patients could guide therapeutic choice, whereby, ERlow mRNA TNBC tumors could respond to epigenetic therapy followed by antiestrogen while ERhigh mRNA TNBC tumors could respond to a proteosome inhibitor followed by antiestrogen therapy. These results identify a novel epigenetic biomarker as predictive of therapeutic response.

Citation Format: Christina A. von Roemeling, Laura A. Marlow, James Miller, Adam Mathias, Louis Dawson, Steadman Harrison, Beth A. Hollister, Derek C. Radisky, John Alton Copland. Estrogen receptor mRNA-directed therapy for triple-negative breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-95. doi:10.1158/1538-7445.AM2014-LB-95

Abstract B298: The controlled local expression of IL-12 as an immunotherapeutic treatment of glioma through the use of the Rheoswitch Therapeutic System® (RTS®) platform

The challenges of developing immunotherapies to treat glioma include the immune- privileged status of the CNS and the physiological processes that contribute to the suppression of immune responses in the brain. The paucity of dendritic cells (DC) in the brain combined with lack of lymphatic drainage, the production of inflammatory mediators, and the physical blood-brain barrier provide several challenges in eliciting tumor specific responses. We have previously assessed the safety and biologic activity of two different RheoSwitch Therapeutic System® (RTS®) controlled IL-12 expression-based therapeutic candidates in Phase I clinical trials for the treatment of metastatic melanoma: AD-RTS-hIL-12 (AD) and DC-RTS-hIL-12 (DC), along with the activator ligand veledimex, also known as INXN 1001 (AL). Based upon preliminary favorable results observed for these two product candidates, we chose to study the activity of RTS-mIL-12 delivered intratumorally by either a dendritic cell or an adenoviral vector-based approach in an orthotopic murine glioma model. The ability and the extent of AL to cross the blood brain barrier (BBB) were assessed in both C57B6 mice and cynomolgus monkeys. The results in mice demonstrated that AL crosses the BBB (peak and trough level of 67-16 ng/mL in cerebral spinal fluid (CSF) over the dose range of 450-900 mg/m2/day) which exceeded tumor AL levels previously shown to induce the production of mIL-12 and resulted in a &gt;50% tumor growth inhibition in the 4T1 mouse model. AL also crossed the BBB in a similar fashion in the cynomolgus monkey. The effects of DC and AD on survival were assessed in the mouse orthotopic GL261 glioma model where each animal received 1 x 105 GL261 glioma cells via intracranial injection (i.c.) on Day 0. In this study murine dendritic cells were transduced at increasing multiplicity of infection (MOI) of 100, 500, 1,000, 5,000, or 10,000 of AD vector particles (vp)/cell. The transduced DC's were intratumorally (i.t.) administered at 1 x 106 DC /animal, on Day 5. AD was administered i.t. at 1 x 108, 5 x 108, 1 x 109, or 5 x 109 vp/animal on Day 5. AL was administered ad libitum in the chow starting on Day 4 (∼675 mg/m2/day) and continued for the duration of the study. DC + AL or AD + AL both clearly demonstrated a dose-related increase in survival benefit without exhibiting an adverse safety profile. All animals treated with DC &gt; 5000 MOI + AL or AD 5 x 109 vp + AL survived throughout the duration of the study (100% survival at 75 days) with no adverse clinical signs observed. In contrast, the mean survival in the control groups was 22 ± 3 days. Additional studies in this model are ongoing to determine the optimal dose and schedule. This novel regulated immunotherapeutic approach could potentially be translated into an effective clinical regimen for the treatment of glioma.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B298.

Citation Format: John A. Barrett, Lei Sun, Charles Reed, Laurent Humeau, Francois Lebel, Beth A. Hollister, Kay R. Meshaw, Jon Lewis. The controlled local expression of IL-12 as an immunotherapeutic treatment of glioma through the use of the Rheoswitch Therapeutic System® (RTS®) platform. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B298.

Accelerating drug discovery for Alzheimer's disease: best practices for preclinical animal studies

Animal models have contributed significantly to our understanding of the underlying biological mechanisms of Alzheimer's disease (AD). As a result, over 300 interventions have been investigated and reported to mitigate pathological phenotypes or improve behavior in AD animal models or both. To date, however, very few of these findings have resulted in target validation in humans or successful translation to disease-modifying therapies. Challenges in translating preclinical studies to clinical trials include the inability of animal models to recapitulate the human disease, variations in breeding and colony maintenance, lack of standards in design, conduct and analysis of animal trials, and publication bias due to under-reporting of negative results in the scientific literature. The quality of animal model research on novel therapeutics can be improved by bringing the rigor of human clinical trials to animal studies. Research communities in several disease areas have developed recommendations for the conduct and reporting of preclinical studies in order to increase their validity, reproducibility, and predictive value. To address these issues in the AD community, the Alzheimer's Drug Discovery Foundation partnered with Charles River Discovery Services (Morrisville, NC, USA) and Cerebricon Ltd. (Kuopio, Finland) to convene an expert advisory panel of academic, industry, and government scientists to make recommendations on best practices for animal studies testing investigational AD therapies. The panel produced recommendations regarding the measurement, analysis, and reporting of relevant AD targets, th choice of animal model, quality control measures for breeding and colony maintenance, and preclinical animal study design. Major considerations to incorporate into preclinical study design include a priori hypotheses, pharmacokinetics-pharmacodynamics studies prior to proof-of-concept testing, biomarker measurements, sample size determination, and power analysis. The panel also recommended distinguishing between pilot 'exploratory' animal studies and more extensive 'therapeutic' studies to guide interpretation. Finally, the panel proposed infrastructure and resource development, such as the establishment of a public data repository in which both positive animal studies and negative ones could be reported. By promoting best practices, these recommendations can improve the methodological quality and predictive value of AD animal studies and make the translation to human clinical trials more efficient and reliable.

Corticorelin acetate, a synthetic corticotropin-releasing factor with preclinical antitumor activity, alone and with bevacizumab, against human solid tumor models

PURPOSE

Corticorelin acetate (CrA) is a synthetic form of corticotropin-releasing factor undergoing clinical trials in the treatment of peritumoral brain edema (PBE). We sought to investigate preclinically its potential as an antitumor agent against human solid tumors and to assess its ability to enhance the therapeutic activity of bevacizumab (BEV) in these same models.

METHODS

The in vivo efficacy of CrA as a single agent and in combination with the antiangiogenic agent, BEV, was examined in two preclinical human tumor models, the MX-1 breast and Colo-205 colon carcinomas. These models were selected based on their known sensitivity to BEV and were tumor types in which BEV has been approved for clinical use. The corneal micropocket assay was also performed to assess the antiangiogenic activity of CrA relative to BEV. The exposure level of CrA in the mouse using a typical preclinical regimen was measured so as to compare it to reported clinical exposure levels.

RESULTS

CrA was active as a single agent in the MX-1 breast carcinoma, but did not exhibit statistically significant activity as a single agent in the Colo-205 colon carcinoma under the doses and schedules used in the study. When BEV, which was active or near active in both the MX-1 and Colo-205 models, was administered concomitantly with CrA, therapeutic outcomes were observed that were significantly better than those obtained using either monotherapy. These therapeutic potentiations using CrA plus BEV were obtained in the absence of any observable increase in toxicities. CrA was active in the corneal micropocket assay, producing a substantial (>70%) inhibition of neovascularization. A representative CrA regimen in mice produced an exposure within eightfold of human exposure determined at one-half the current clinical dose.

CONCLUSIONS

The application of CrA for the treatment of PBE likely involves its activity as an antiangiogenic agent, which may be one possible mechanism to explain its observed preclinical antitumor activity. That activity, as well as its ability to provide an enhanced therapeutic outcome when given in conjunction with BEV in the absence of increased toxicity, supports the use of CrA clinically as other than a replacement therapy for dexamethasone in PBE.

Abstract 5095: Differential sensitivity to dietary restriction in xenograft models harboring PI3K pathway mutations in nude mice

The inhibitory effect of dietary restriction on the growth of human tumors has been well established. Recent evidence exploring the molecular mechanisms underlying this observation has been accumulating and supports a strong link with the PI3K/PTEN signaling pathway. Despite these recent advances, there remains a significant gap in our understanding of this observation. We have investigated the effects of dietary restriction on tumor growth in nude mouse xenografts of human tumor cell lines containing mutations in either PI3K or PTEN. In these experiments, dietary restriction was started after mean tumor size had reached between 60-100mg and continued until control groups reached endpoint (1000-2000mg). Diet restriction was achieved by feeding the experimental group a vitamin and nutrient enriched chow at a 20-40% reduction in overall amount relative to control groups. Our findings suggest that while activation of the PI3K/PTEN pathway may afford some resistance to dietary restriction, there may be other underlying mechanisms involved.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5095.

Abstract 1554: Corticorelin acetate, a synthetic corticotropin releasing factor, demonstrates antiangiogenic and antitumor activity alone and enhances bevacizumab activity in human tumor models

Corticorelin acetate (CrA) is a synthetic form of corticotropin-releasing factor undergoing clinical trials in the treatment of peritumoral brain edema (PBE). A corneal micropocket angiogenesis assay (CMA) was performed to assess the activity of CrA relative to bevacizumab (BEV). We also investigated the in vivo anti-tumor efficacy of CrA as a single agent and in combination with BEV, in two preclinical human tumor models, the MX-1 breast and Colo-205 colon carcinomas. These models were selected based on their sensitivity to BEV.

In the CMA, six groups of female mice were implanted with pellets containing VEGF or no VEGF, and treated for 7 days. The vehicle control group received phosphate buffered saline, sc, bid. The positive reference group received BEV, ip, qd, at 5 mg/kg/inj. The two remaining groups received CrA sc, bid, at 0.1 mg/kg/inj or 0.2 mg/kg/inj. Treatment outcome was determined from semi-quantitative characterization of neovascularization. CrA produced a substantial (&gt;70%) inhibition of neovascularization (p&lt;0.01) in the CMA.

In the xenograft studies, mice were implanted sc in the flank with approximately 1 mm3 tumor fragments obtained from donor passage mice (MX-1), or with 1 × 106 tissue culture-derived Colo-205 cells implanted in 50% matrigel. When tumors were generally between 80-240 mg (mm3), mice were distributed to control and treatment sets. CrA was administered at two dose levels, 0.1 and 0.2 mg/kg/injection, sc, twice daily (bid). BEV was administered at a dose of 5 mg/kg/inj, ip, twice weekly. All treatments were continued until each group achieved its tumor target size, 1 gm in the Colo-205 experiment, and 1.5 gm in the MX-1 experiment. A log cell kill (LCK) of ≥1.0, equivalent to a delay in tumor growth of ≥ 3.32 x tumor volume doubling time, accompanied by statistical significance (p&lt;0.05) was considered indicative of activity.

CrA was active as a single agent in the MX-1 breast carcinoma (1.0 LCK; p&lt;0.02), but inactive in the Colo-205 colon carcinoma. BEV was active (1.1 LCK; p&lt;0.002) or near active (0.9 LCK; p&lt;0.001) in both the MX-1 and Colo-205 models, respectively. When BEV was administered concomitantly with CrA, therapeutic outcomes were observed that were significantly better (3.3 LCK in MX-1, p&lt;0.03; 1.9 LCK in Colo-205, p&lt;0.01) than those obtained using either monotherapy. These therapeutic potentiations using CrA plus BEV were obtained in the absence of any observable increase in toxicities.

Conclusion: CrA has demonstrated anti-angiogenic activity in vivo, which may be one possible mechanism to explain its observed preclinical antitumor activity. Importantly it enhances the antitumour activity of BEV in both MX-1 and Colo-205 models. Given the good safety profile of CrA and its lack of hypertensive side effects in clinical trials, CrA should be evaluated clinically in combination with BEV.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1554.

Acyl Sulfonamide Anti-Proliferatives: Benzene Substituent Structure−Activity Relationships for a Novel Class of Antitumor Agents

Two closely related diaryl acylsulfonamides were recently reported as potent antitumor agents against a broad spectrum of human tumor xenografts (colon, lung, breast, ovary, and prostate) in nude mice. Especially intriguing was their activity against colorectal cancer xenografts. In this paper, rapid parallel synthesis along with traditional medicinal chemistry techniques were used to quickly delineate the structure-activity relationships of the substitution patterns in both phenyl rings of the acylsufonamide anti-proliferative scaffold. Although the molecular target of the compounds remains unclear, we determined that the vascular endothelial growth factor-dependent human umbilical vein endothelial cells assay in combination with a soft agar disk diffusion assay allowed for optimization of potency in the series. The pharmacokinetic properties and in vivo activity in an HCT116 xenograft model are reported for representative compounds.

GEM 231, a second-generation antisense agent complementary to protein kinase A RIalpha subunit, potentiates antitumor activity of irinotecan in human colon, pancreas, prostate and lung cancer xenografts

GEM 231, a second-generation antisense oligonucleotide targeted against the RIalpha subunit of protein kinase A (PKA) was co-administered with the chemotherapeutic agent irinotecan, a topoisomerase-I inhibitor, to study the antitumor efficacy of the combination in nude mice bearing various human tumor xenografts. The combination treatment of GEM 231 and irinotecan produced enhanced and prolonged tumor-growth inhibition, compared with irinotecan monotherapy, against human colon (HCT-116), pancreas (Panc-1), prostate (PC3) and lung (SKMES) tumors in mice. The extent of tumor-growth inhibition, however, varied among the different tumor models studied. The tumor-growth inhibition depended on the dose of GEM 231 co-administered with irinotecan. The combination of GEM 231 (20 mg/kg, i.p., 5 days on 2 days off x 7) and irinotecan (50 mg/kg, i.v., qwk x 3) produced significantly longer tumor-growth delay than did irinotecan administered alone. Importantly, the co-administration of irinotecan and GEM 231 did not result in higher toxicity compared with monotherapies in the several tumor models tested. These results suggest that the use of irinotecan in combination with GEM 231 may increase the therapeutic index of irinotecan in cancer patients.

Potentiation of antitumor activity of irinotecan by chemically modified oligonucleotides

Co-administration of synthetic chemically modified oligonucleotides with irinotecan, a selective topoisomerase I inhibitor, provided a significant enhancement in the antitumor activity of irinotecan. The enhancement of antitumor activity of irinotecan with co-administration of chemically modified oligonucleotides was observed in several tumor models--pancreatic cancer (Panc-1), colon cancer (HCT-116) and melanoma (A375). Inhibition of tumor growth in all three models required the co-administration of irinotecan and chemically modified oligonucleotides, but was independent of the nucleotide sequence of the oligonucleotides. The potentiation of antitumor activity was dependent on the dose of irinotecan and chemically modified oligonucleotides administered. The enhancement of antitumor activity of irinotecan was also observed by co-administration of a phosphorothioate oligonucleotide, however, to a lesser extent than did chemically modified oligonucleotides, suggesting that metabolic stability of the oligonucleotide contributes to the enhancement of antitumor activity seen with irinotecan. The co-administration of dextran sulfate sodium with irinotecan showed insignificant potentiation of antitumor activity of irinotecan, suggesting that the enhancement of antitumor activity of irinotecan observed was not a result of polyanionic characteristic of oligonucleotides. Co-administration of irinotecan and chemically modified oligonucleotides did not result in increased toxicity in the tumor models studied. Potentiation of antitumor activity of irinotecan observed with co-administration of oligonucleotides suggests that the oligonucleotides affect the pharmacokinetics and/or metabolism of irinotecan. The use of chemically modified oligonucleotides together with irinotecan may increase the therapeutic index of irinotecan in cancer patients and continued development of such agents should be considered.