Abstract P3-06-05: Receptor-mediated binding of HER2-targeted antibody-liposomal doxorubicin conjugate MM-302 increases liposome binding, nuclear doxorubicin, DNA damage and efficacy relative to untargeted PEGylated liposomal doxorubicin (PLD/Doxil)

This abstract was withdrawn by the authors.

Abstract P4-21-40: In vitro and in vivo activity of HER2-targeted antibody-liposomal doxorubicin conjugate MM-302 in HER2-intermediate tumors

This abstract was withdrawn by the authors.

MP6: HOMOCYSTEINE LEVEL IN PFO RELATED STROKE PATIENTS WITH RESPECT TO MEDICAL THERAPY VS PFO CLOSURE

Purpose of Study

Homocysteine is an independent risk factor of ischemic stroke by promoting vascular endothelial dysfunction and thrombotic process through oxidative stress. We previously found that PFO closure may reduce total homocysteine level (tHcy) in plasma. Here, we compare the effect of PFO closure and medical treatment in reducing mild homocysteinemia in PFO-related stroke patients.

Methods Used

28 PFO-related stroke patients with mildly elevated tHcy (>12 µmol/l) were prospectively recruited in accordance with IRB. 14 received PFO closure and 14 were treated by medical therapy (antiplatelet/anticoagulant) alone. None of the patients were on folate or vitamin B supplementation. Plasma was collected at baseline and 1 year follow-up after treatment. tHcy level was determined by selected reaction monitoring using mass spectrometry.

Summary of Results

Compared to medical therapy, PFO closure resulted in a lower tHcy level during follow-up (PFO closure: 11.13±3.94 µmol/L, medical therapy: 15.48±3.55 µmol/L, p=0.006), with no difference at baseline (PFO closure: 17.77±4.39 µmol/L, medical therapy: 16.47±7.50 µmol/L, p=0.575). Mild hyperhomocysteinemia patients post PFO closure had a significant reduction of tHcy by 37.34% (p=0.0005), with 71.43% of the patients (10 of 14) having tHcy levels back to normal (<12 µmol/l), while most of medically treated patients (13 of 14) stayed abnormal (p=0.4820) (χ2-test, adjusted p=0.002).

Conclusions

We found that compared with routine medical therapy, PFO closure reduced tHcy level in patients with mild hyperhomocysteinemia. Since PFO stroke patients tend to be younger, the life-time risk of even mildly elevated tHcy may be important for future thrombotic risk. Understanding the mechanism of PFO-related tHcy changes is important in optimizing medical treatment (e.g, folate replacement); studies are ongoing.

Abstract MP6 Figure 1

MP13: IMPORTANT ROLE OF PROTHROMBIN TIME (PT) AND PARTIAL THROMBOPLASTIN TIME (PTT) IN PREDICTING TPA-RELATED HEMORRHAGIC TRANSFORMATION

Purpose of Study

IV tPA is not routinely followed by blood work due to its reputed short half life. While there has been much focus on tPA's extra-vascular effects on the neurovascular unit in the context of hemorrhagic transformation (HT), little is known about its intravascular efficacy, where it has its intended effect. Emerging data suggest that tPA may be most effective in microvasculature and IV therapy may be a good adjunct to intra-arterial therapy. We previously found that the effect of tPA can last more than 72 hr after stroke onset. Now, we report that even routine blood labs can potentially predict HT.

Methods Used

72 storke patients with IV tPA were recruited on IRB approval. Clinical coagulation profile (PT, PTT, fibrinogen and D-dimer) were performed at 12, 24, 72 hr post tPA. Patients on medications (e.g. anticoagulants) or with conditions (e.g. liver dysfunction, infection) that may affect these labs were excluded.

Summary of Results

Compared to those without HT, HT patients had significantly higher PT and PTT (Fig A,B) as early as 12 hr post IV tPA and throughout the first 3 days of treatment. ROC analysis suggested PT/PTT at 12 and 24 hr has potential to predict tPA-induced HT (Fig C,D. PT: AUC=0.848, p=0.001; PTT: AUC=0.877; p=0.003).

Conclusions

Higher PT/PTT level within 72 hr of IV tPA is early marker of tPA-induced HT. Whether these routine labs have value in symptomatic hemorrhage will require further study in a larger cohort. But this proof-of-concept study suggests that tPA efficacy can potentially be followed in real time. The development of a reliable blood test would be of clinical utility to gauge thrombolytic efficacy in real time to guide and triage adjunct treatments.

Abstract MP13 Figure 1

15: PFO CLOSURE REDUCES PLASMA LEVELS OF SEROTONIN IN A LONG TERM FOLLOWUP OF STROKE PATIENTS

Purpose of Study

PFO allows venous clots and vasoactive factors to bypass pulmonary filtration and remain in circulation. We previously identified an immediate reduction of procoagulant serotonin (5-HT) in left atrial blood post PFO closure. To understand the long-term effect of PFO closure, we report the change of 5-HT in peripheral venous blood in 1-year followup.

Methods Used

97 PFO-related stroke patients were recruited on IRB approval. Venous blood was collected at baseline (BL) and 1 year follow-up (FU) of treatments (PFO closure and medical therapy). Plasma 5-HT was quantified by mass spectrometry. Patients with serotonin modifying medications (ie. SSRIs) or conditions (anxiety/depression) were excluded.

Summary of Results

5-HT level in peripheral venous blood was significantly reduced by 27.27% (BL: 7.57±8.04 µM; FU: 5.51±5.72 µM; p=0.0034) in 61 patients receiving PFO closure (figure 1A). In the 37 PFO patients treated with medicine alone, no changes were observed (BL: 5.79±7.15 µM; FU: 6.25±6.68 µM; p=0.4050) (figure 1B). 5-HT reduction was independently associated with PFO closure after adjusting for age, gender, medical history and medication status in a multivariate regression (figure 1C).

Conclusions

We found that PFO closure independently reduced 5-HT level in peripheral venous blood. These results support the hypothesis that PFO related right-to-left interatrial shunt may foster higher level of procoagulant and vascoactive substances in circulation. While PFO closure decrease prothrombotic markers immediately post closure, this effect is sustained in long term followup up to 1 year. Further studies on the clinical outcome of these PFO patients with respect to their prothrombotic circulatory profiles are ongoing.

Abstract 15 Figure 1

Abstract OT3-01-01: HERMIONE: A phase 2, randomized, open label trial comparing MM-302 plus trastuzumab with chemotherapy of physician's choice plus trastuzumab, in anthracycline naive HER2-positive, locally advanced/metastatic breast cancer patients previously treated with pertuzumab and ado-trastuzumab emtansine (T-DM1)

Background: Although HER2-targeted therapies such as pertuzumab and T-DM1 have improved patient outcomes, treatment resistance typically occurs. MM-302 is a HER2-targeted liposomal doxorubicin in development by Merrimack Pharmaceuticals. In a Phase 1 study, patients with HER2-positive metastatic breast cancer (MBC) were treated with MM-302 alone and in combination with trastuzumab with or without cyclophosphamide. MM-302 had an acceptable safety profile and promising efficacy was observed in patients not previously exposed to an anthracycline.

Trial design: HERMIONE (NCT02213744) is a randomized Phase 2, two-arm, open-label trial designed to evaluate if MM-302 can address an unmet medical need in patients with anthracycline naïve, trastuzumab-, pertuzumab- and T-DM1-pretreated HER2-positive locally advanced breast cancer (LABC)/MBC. Patients are randomized 1:1 to receive MM-302 (30mg/m2, Q3W) plus trastuzumab (6mg/kg, Q3W) or chemotherapy of physician's choice (vinorelbine, capecitabine, or gemcitabine) plus trastuzumab (6mg/kg, Q3W).

Eligibility criteria: Centrally confirmed HER2-positive LABC/MBC, no prior anthracycline exposure, prior trastuzumab in any setting, prior pertuzumab and T-DM1 in the LABC/MBC setting, unlimited prior lines of therapy, ECOG 0-1 and LVEF ≥50%. CNS metastases are permitted if stable and without symptoms or steroids for 4 weeks.

Specific aims: The primary endpoint is independently assessed progression free survival (PFS). Secondary endpoints include investigator assessed PFS, overall survival, response rate, safety and patient related outcomes.

Statistics: 250 patients will be enrolled to observe 191 PFS events for 90% power to detect a Hazard Ratio of 0.625. The MM-302 arm will be compared to the control arm on the primary endpoint of PFS using a stratified log-rank test at one-sided 0.025 level.

Accrual status: First patient in was December 2014 and enrollment is expected to be complete in late 2016. Sites are open in the US, Canada and Western Europe and are currently enrolling patients.

Citation Format: Miller K, Cortes J, Hurvitz SA, Krop IE, Tripathy D, Verma S, Riahi K, Reynolds JG, Wickham T, Molnar I, Yardley DA. HERMIONE: A phase 2, randomized, open label trial comparing MM-302 plus trastuzumab with chemotherapy of physician's choice plus trastuzumab, in anthracycline naive HER2-positive, locally advanced/metastatic breast cancer patients previously treated with pertuzumab and ado-trastuzumab emtansine (T-DM1). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT3-01-01.

Abstract T P347: Metabolomic Analysis of PFO-Related Stroke Shows Immediate and Persistent Decrease of Homocysteine Post PFO Closure

Background: PFO, an independent stroke risk factor, enables direct mixing of venous and arterial circulation. As we have found previously, PFO serves not only as a conduit for venous clots, but also enables harmful factors such as serotonin (5HT) to avoid pulmonary filtration to remain within circulation at elevated levels, potentially contributing to a prothrombotic state. We hypothesize that in addition to 5HT, other factors may also be involved. In the context of endovascular PFO closure, a bedside model to understand PFO circulatory signaling, we performed a full metabolomic profile of mediators that may respond to PFO closure.

Method: Non-migraine stroke patients were recruited in accordance with IRB approval, plasma was sampled from left and right atria pre and post closure and also from venous blood 3 months post PFO closure. A discovery metabolite screening was performed in 14 patients who underwent PFO closure, and analysis was performed using one-way ANOVA.

Result: After stringent data filtering (537 metabolites, one-way ANOVA, p-value <0.01), we identified significant changes in a panel of small molecules after PFO closure - the most prominent change being in homocysteine (HCY). While relative HCY levels (expressed as peak area) in the left atrium (LA) and right atrium (RA) were comparable pre-closure (pre-LA: 5.61 ± 0.09; pre-RA: 5.30 ± 0.48), HCY immediately decreased in LA post PFO closure (post-LA: 4.56 ± 0.04) and HCY level remained low in peripheral venous blood at 3-month follow-up (4.57 ± 0.06; p = 0.0036).

Conclusion: We found PFO closure to lower HYC immediately in left atrial (arterial) blood, and this effect persists in peripheral venous circulation at 3 months post procedure. Since high level of HYC is independently associated with stroke and heart disease, our results suggest that mechanical PFO repair may improve circulatory profile of PFO stroke patients. Studies in a larger patient cohort and validation of other important metabolites are ongoing.

Abstract P4-12-29: Assessment of safety and activity in an expanded phase 1 study of MM-302, a HER2-targeted liposomal doxorubicin, in patients with advanced HER2-positive (HER2+) breast cancer

Background: MM-302 is a novel antibody drug conjugate (ADC) combining PEGylated liposomal doxorubicin with anti-HER2 scFvs. MM-302 was designed to overcome the limitations associated with using anthracyclines in the treatment of HER2-positive breast cancer. Anthracyclines have been an effective backbone of breast cancer therapies for decades. However, cardiotoxicity issues associated with free anthracyclines have limited their effective use. While liposomal doxorubicin formulations have succeeded in reducing cardiotoxicity, they have failed to demonstrate clear-cut efficacy advantages. MM-302 specifically targets tumor cells overexpressing HER2 with minimal uptake into normal cells such as cardiomyocytes which express low levels of HER2. This Phase 1 study evaluates the safety of MM-302 in patients with HER2+ advanced breast cancer.

Methods: Patients aged ≥ 18 years with histologically confirmed HER2+ advanced breast cancer that have progressed or recurred on standard therapy or for which no standard therapy exists having measurable disease, adequate performance status, bone marrow reserve and organ function, were eligible for the study. A post-treatment biopsy was required. A 3 + 3 dose escalation design (8, 16, 30, 40 and 50 mg/m2 administered i.v. q4w) is used to identify a Phase 2 dose followed by expansion arms at 40 and 50 mg/m2 for a preliminary indication of activity. Secondary endpoints included determination of dose-limiting toxicity, adverse event(s), and PK of MM-302, as well as overall response and clinical benefit rates of MM-302.

Results: We report data from MM-302 dose levels (30, 40 and 50 mg/m2 as monotherapy) that are expected to be therapeutically relevant. Eight patients dosed at presumed sub-therapeutic dose levels of 8 and 16 mg/m2 were excluded from the efficacy analysis. Patients had received a median of 9.5 prior agents (range 3-19) in all settings. All patients had been treated with trastuzumab, 96% with prior taxanes, 67% lapatinib, 54% anthracyclines and 33% T-DM1. At the time of this analysis (n = 27), overall response rate was 17% (4 out of 24 evaluable patients) and the estimated median Progression Free Survival (PFS) was 5.7 months, with six patients still receiving treatment. Eight patients (30%) had a PFS of greater than 6.0 months. Neutropenia was the most common treatment-related grade 3/4 toxicity and occurred in 15% of patients. The most common adverse events include fatigue, nausea, vomiting, and decreased appetite. Constipation, stomatitis, headache and rash were also observed in greater than 20% of patients. No patients discontinued treatment for toxicity. There was no protocol defined cardiotoxicity observed across all dose cohorts and five patients have had cumulative anthracycline exposure exceeding 550 mg/m2 without a reduction in left ventricular ejection fraction.

Conclusion: Overall MM-302 appears to be well tolerated with promising activity in this ongoing trial. Further development is continuing combining MM-302 with trastuzumab and/or cyclophosphamide. In addition, we are evaluating the use of PET imaging to correlate liposomal tumor deposition as an additional potential patient preselection strategy.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-12-29.

Abstract P4-02-05: A novel 64Cu-liposomal PET agent (MM-DX-929) predicts response to liposomal chemotherapeutics in preclinical breast cancer models

Background: Liposomal anthracyclines (such as pegylated liposomal doxorubicin (PLD) or HER2-targeted liposomal doxorubicin (MM-302)) are being used and/or evaluated for the clinical management of breast cancer, but responses vary from patient to patient. It is hypothesized that variability in the deposition of liposomal therapeutics within tumors leads to differences in drug exposure, thereby directly influencing tumor response. We have developed MM-DX-929, a novel 64Cu-liposomal PET imaging agent, as a clinically-implementable tool to investigate whether image-based quantification of liposome deposition in tumors can predict treatment response to liposomal chemotherapeutics, including PLD, MM-302 and/or liposomal irinotecan (MM-398).

Objectives: Our primary objective is to demonstrate that the extent of tumor uptake of MM-DX-929 is predictive of tumor response to MM-302 in preclinical breast cancer xenograft models. A secondary objective is to enable clinical translation of MM-DX-929 to enable incorporation into existing therapeutic trials.

Methods: Mice bearing BT474-M3 mammary and subcutaneous tumors were injected intravenously with MM-DX-929 prior to dosing with MM-302. PET/CT imaging was performed at 16h post MM-DX-929 injection, and tumor uptake was determined. Response to treatment was quantified as tumor volume changes measured over a 2-month period by MRI.

Results: Tumor deposition of MM-DX-929 administration correlated well with treatment response to MM-302 (Spearman correlation coefficient of −0.891 and a p-value of 0.0004). MM-DX-929 accumulation in tumors prior to the start of the MM-302 treatment successfully predicted improved tumor growth inhibition following MM-302 treatment.

Conclusion: These findings support trials of MM-DX-929 as a predictive imaging agent to select patients who are most likely to respond to liposomal therapies. The clinical development of MM-DX-929 for identification of breast cancer patients likely to respond to liposomal therapeutics is currently being pursued.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-02-05.

Head injuries in infants: the risks of bouncy chairs and car seats

AIMS

To establish whether the incorrect use of bouncy chairs (BC) and car seats (CS) is a significant cause of injuries in babies.

METHODS

Prospective study over a 12 month period. All babies under the age of 1 year, presenting to the department with a head injury were eligible.

RESULTS

A total of 131 cases were recorded, 17 (13%) of which were associated with either BC or CS, the second largest aetiological group. All BC cases (11/11, 100%) were caused by a fall from a surface with the baby in the chair. In the CS group, 2/6 (33%) were caused by such a fall. The carer was aware in only one of the 13 cases involving a fall from a surface that there was any chance of injury from this mechanism.

CONCLUSION

Falls from inappropriately placed bouncy chairs or car seats form a significant proportion of head injuries in infants, resulting in unnecessary and preventable morbidity.

Adenovirus as a gene therapy vector for hematopoietic cells

Adenovirus (Adv)-mediated gene transfer has recently gained new attention as a means to deliver genes for hematopoietic stem cell (HSC) or progenitor cell gene therapy. In the past, HSCs have been regarded as poor Adv targets, mainly because they lack the specific Adv receptors required for efficient and productive Adv infection. In addition, the nonintegrating nature of Adv has prevented its application to HSC and bone marrow transduction protocols where long-term expression is required. There is even controversy as to whether Adv can infect hematopoietic cells at all. In fact, the ability of Adv to infect epithelium-based targets and its inability to effectively transfect HSCs have been used in the development of eradication schemes that use Adv to preferentially infect and "purge" tumor cell-contaminating HSC grafts. However, there are data supporting the existence of productive Adv infections into HSCs. Such protocols involve the application of cytokine mixtures, high multiplicities of infection, long incubation periods, and more recently, immunological and genetic modifications to Adv itself to enable it to efficiently transfer genes into HSCs. This is a rapidly growing field, both in terms of techniques and applications. This review examines the two sides of the Adv/CD34 controversy as well as the current developments in this field.

Optimizing cardiovascular gene therapy: increased vascular gene transfer with modified adenoviral vectors

BACKGROUND

Adenovirus is widely used as a vector for gene transfer to the vasculature. However, the efficiency of these vectors can be limited by ineffective viral-target cell interactions. Viral attachment, which largely determines adenoviral tropism, is mediated through binding of the adenoviral fiber coat protein to the Coxsackievirus and adenovirus receptor, while internalization follows binding of the adenoviral RGD motif to alpha(v)-integrin receptors. Modifications of the fiber coat protein sequence have been successful for targeting the adenovirus to more prevalent receptors in the vasculature, including heparan sulfate-containing receptors and alpha(v)-integrin receptors.

HYPOTHESIS

Modified adenoviral vectors targeted to receptors more prevalent in the vasculature result in an increased transfer efficiency of the virus in vitro and in vivo even in the presence of clinically relevant doses of heparin.

DESIGN

We tested 2 modified E1- and E3-deleted Ad5 type adenoviral vectors containing the beta-galactosidase gene. AdZ.F(pK7) contains multiple positively charged lysines in the fiber coat protein that target the adenovirus to heparan sulfate receptors, while AdZ.F(RGD) contains an RGD integrin-binding sequence in the fiber coat protein that allows binding to alpha(v)-integrin receptors. The gene transfer efficiency of these modified viruses was compared in rat aortic smooth muscle cells in vitro and in an in vivo porcine model of balloon-induced arterial injury. Because of the use of heparin during most vascular surgical procedures and the concern that heparin might interfere with the binding of AdZ.F(pK7) to heparan sulfate receptors, the effect of heparin on the in vitro and in vivo transfer efficiency of these 2 modified adenoviruses was evaluated.

RESULTS

In vitro infection of rat aortic smooth muscle cells with AdZ.F(pK7) and AdZ.F(RGD) resulted in significantly higher levels of beta-galactosidase expression compared with the unmodified adenovirus (mean +/- SEM, 1766.3 +/- 89.1 and 44.8 +/- 3.4 vs 10.1 +/- 0.7 mU per milligram of protein; P<.001). Following heparin administration, the gene transfer efficiency achieved with AdZ.F(pK7) diminished slightly in a concentration-dependent manner. However, the transfer efficiency was still greater than with the unmodified virus (mean +/- SEM, 1342.3 +/- 101.8 vs 4.8 +/- 0.4 mU per milligram of protein; P<.001). In vivo, following injury to the pig iliac artery with a 4F Fogarty balloon catheter, we found that AdZ.F(pK7) transduced the artery approximately 35-fold more efficiently than AdZ.F and 3-fold more efficiently than AdZ.F(RGD) following the administration of intravenous heparin, 100 U/kg body weight, and heparinized saline irrigation.

CONCLUSIONS

Modifications of the adenovirus that lead to receptor targeting resulted in significantly improved gene transfer efficiencies. These improvements in transfer efficiencies observed with the modified vectors decreased slightly in the presence of heparin. However, AdZ.F(pK7) was still superior to AdZ.F(RGD) and AdZ.F despite heparin administration. These data demonstrate that modifications of adenoviral vectors that enhance binding to heparan sulfate receptors significantly improve gene transfer efficiency even in the presence of heparin and suggest an approach to optimize gene transfer into blood vessels.

The murine CAR homolog is a receptor for coxsackie B viruses and adenoviruses

Complementary DNA clones encoding the murine homolog (mCAR) of the human coxsackievirus and adenovirus receptor (CAR) were isolated. Nonpermissive CHO cells transfected with mCAR cDNA became susceptible to infection by coxsackieviruses B3 and B4 and showed increased susceptibility to adenovirus-mediated gene transfer. These results indicate that the same receptor is responsible for virus interactions with both murine and human cells. Analysis of receptor expression in human and murine tissues should be useful in defining factors governing virus tropism in vivo.

Multiple adenovirus serotypes use alpha v integrins for infection

The nucleotide sequence encoding the penton base integrin-binding domains of several human adenoviruses was obtained by homology PCR. Each of the penton base proteins contains a conserved Arg-Gly-Asp (RGD) sequence that is predicted to lie at the apex of two extended alpha helices. The penton base RGD domain promotes efficient infection of host cells by multiple adenovirus serotypes via interaction with alpha v integrins, thus indicating that alpha v integrins play a central role in the entry of adenoviruses into host cells.

Bioreactor development for production of viral pesticides or heterologous proteins in insect cell cultures

The insect cell-baculovirus expression system has significant potential for producing proteins requiring some degree of posttranslational modification. T. ni cells appear to be as good a host as S. frugiperda cells for heterologous protein production as demonstrated by production of beta-galactosidase. Attachment-dependent cells of T. ni can be effectively cultured in a packed-bed reactor using glass beads. When cell in such a reactor were infected, they produced 35% of the total protein as beta-galactosidase. No cell detachment was observed even 70 h postinfection. A model of viral entry has been proposed and tested.