Carbon dioxide increases with face masks but remains below short-term NIOSH limits

BACKGROUND AND PURPOSE

COVID-19 pandemic led to wide-spread use of face-masks, respirators and other personal protective equipment (PPE) by healthcare workers. Various symptoms attributed to the use of PPE are believed to be, at least in part, due to elevated carbon-dioxide (CO2) levels. We evaluated concentrations of CO2 under various PPE.

METHODS

In a prospective observational study on healthy volunteers, CO2 levels were measured during regular breathing while donning 1) no mask, 2) JustAir® powered air purifying respirator (PAPR), 3) KN95 respirator, and 4) valved-respirator. Serial CO2 measurements were taken with a nasal canula at a frequency of 1-Hz for 15-min for each PPE configuration to evaluate whether National Institute for Occupational Safety and Health (NIOSH) limits were breached.

RESULTS

The study included 11 healthy volunteers, median age 32 years (range 16-54) and 6 (55%) men. Percent mean (SD) changes in CO2 values for no mask, JustAir® PAPR, KN95 respirator and valve respirator were 0.26 (0.12), 0.59 (0.097), 2.6 (0.14) and 2.4 (0.59), respectively. Use of face masks (KN95 and valved-respirator) resulted in significant increases in CO2 concentrations, which exceeded the 8-h NIOSH exposure threshold limit value-weighted average (TLV-TWA). However, the increases in CO2 concentrations did not breach short-term (15-min) limits. Importantly, these levels were considerably lower than the long-term (8-h) NIOSH limits during donning JustAir® PAPR. There was a statistically significant difference between all pairs (p < 0.0001, except KN95 and valved-respirator (p = 0.25). However, whether increase in CO2 levels are clinically significant remains debatable.

CONCLUSION

Although, significant increase in CO2 concentrations are noted with routinely used face-masks, the levels still remain within the NIOSH limits for short-term use. Therefore, there should not be a concern in their regular day-to-day use for healthcare providers. The clinical implications of elevated CO2 levels with long-term use of face masks needs further studies. Use of PAPR prevents relative hypercapnoea. However, whether PAPR should be advocated for healthcare workers requiring PPE for extended hours needs to evaluated in further studies.

Immune modulation resulting from MR-guided high intensity focused ultrasound in a model of murine breast cancer

High intensity focused ultrasound (HIFU) rapidly and non-invasively destroys tumor tissue. Here, we sought to assess the immunomodulatory effects of MR-guided HIFU and its combination with the innate immune agonist CpG and checkpoint inhibitor anti-PD-1. Mice with multi-focal breast cancer underwent ablation with a parameter set designed to achieve mechanical disruption with minimal thermal dose or a protocol in which tumor temperature reached 65 °C. Mice received either HIFU alone or were primed with the toll-like receptor 9 agonist CpG and the checkpoint modulator anti-PD-1. Both mechanical HIFU and thermal ablation induced a potent inflammatory response with increased expression of Nlrp3, Jun, Mefv, Il6 and Il1β and alterations in macrophage polarization compared to control. Furthermore, HIFU upregulated multiple innate immune receptors and immune pathways, including Nod1, Nlrp3, Aim2, Ctsb, Tlr1/2/4/7/8/9, Oas2, and RhoA. The inflammatory response was largely sterile and consistent with wound-healing. Priming with CpG attenuated Il6 and Nlrp3 expression, further upregulated expression of Nod2, Oas2, RhoA, Pycard, Tlr1/2 and Il12, and enhanced T-cell number and activation while polarizing macrophages to an anti-tumor phenotype. The tumor-specific antigen, cytokines and cell debris liberated by HIFU enhance response to innate immune agonists.

Abstract 3952: Localized nanodelivery combined with immunotherapy promotes curative anti-tumor responses in a murine breast cancer model

Optimal pairing of chemotherapy with immunotherapy can harness potential synergies and augment tumor immunity in solid tumors with low mutation burden by i) reducing tumor bulk, ii) releasing tumor antigen for cross-presentation and cross-priming, iii) releasing cancer-suppressive cytokines/chemokines, and iv) retaining circulating immune cell populations. Temperature-sensitive liposomes (TSL) have the potential to accomplish these goals as ultrasound (US) insonation or other treatment modalities can release the chemotherapy within bulky solid tumors in response to hyperthermia to maximize the local response and minimize off-target effects. Here we used Doxorubicin (Dox), stabilized within the core of TSL by forming a drug complex with copper (CuDox), to mediate immunogenic cell death (ICD) and release of type I interferons (IFNs). This activatable chemotherapy (CuDox-TSL+US) was combined with immunotherapy using CpG-ODN, a toll-like receptor 9 agonist, and a PD-1 antibody (αPD-1) for checkpoint blockade. We assessed the schedule and sequence of the chemo-immunotherapy protocol to maximize therapeutic outcome.

CuDox-TSL were made of DPPC:MPPC:DSPE-PEG2k, 86:10:4 in the presence of copper (II) gluconate and triethanolamine at 0.2 mg-Dox/mg-lipid. Mice with bilateral invasive neu deletion (NDL) tumors (4 mm) were treated with an i.v. administration of CuDox-TSL at 6 mg Dox/kg body weight. One tumor was insonified with a peak ultrasound pressure of 1.1 MPa at a frequency of 1.5 MHz at 42°C for 5 min prior to and 20 min post drug injection with a variable duty cycle. Upon completion of US-hyperthermia, 100 µg of CpG-ODN 1826 was injected intratumorally to the insonified tumor. Three days later αPD-1 (200 µg, i.p.) was administrated.

We found that Dox in combination with hyperthermia induced release of ICD markers and type I IFNs in cell culture of various murine cancer cell lines. Following intravenous administration

of CuDox-TSL, ultrasonic activation of liposomes in the treated tumors promoted release and cross-presentation of a model tumor antigen by antigen-presenting cells in distant tumors. While a variety of chemo-immunotherapy protocols achieved a complete response in more than 50% of treated mice, the complete response rate was greatest (90%) when one week of immunotherapy priming preceded activatable chemotherapeutic administration. Repeated chemotherapeutic delivery, while effectively reducing viable tumor, also reduced efficacy and the fraction of viable CD8+ T-cells as indicated by flow cytometric analysis. Taken together, the results suggest that a single-dose administration of activatable chemotherapy after immune priming enhances survival in a murine model of breast cancer. In clinical practice, however, assessment of macrophage and T-cell populations over the course of treatment could help inform dose timing and number of treatment repetitions.

Citation Format: Azadeh Kheirolomoom, Matthew T. Silvestrini, Elizabeth S. Ingham, Lisa M. Mahakian, Sarah M. Tam, Spencer K. Tumbale, Josquin Foiret, Neil E. Hubbard, Alexander D. Borowsky, William J. Murphy, Katherine W. Ferrara. Localized nanodelivery combined with immunotherapy promotes curative anti-tumor responses in a murine breast cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3952.

A Syngeneic ErbB2 Mammary Cancer Model for Preclinical Immunotherapy Trials

In order to develop a practical model of breast cancer, with in vitro and syngeneic, immune-intact, in vivo growth capacity, we established a primary cell line derived from a mammary carcinoma in the transgenic FVB/N-Tg(MMTV-ErbB2*)NDL2-5Mul mouse, referred to as "NDL^UCD". The cell line is adapted to standard cell culture and can be transplanted into syngeneic FVB/N mice. The line maintains a stable phenotype over multiple in vitro passages and rounds of in vivo transplantation. NDL^UCD tumors in FVB/N mice exhibit high expression of ErbB2 and ErbB3 and signaling molecules downstream of ErbB2. The syngeneic transplant tumors elicit an immune reaction in the adjacent stroma, detected and characterized using histology, immunophenotyping, and gene expression. NDL^UCD cells also express PD-L1 in vivo and in vitro, and in vivo transplants are reactive to anti-immune checkpoint therapy with responses conducive to immunotherapy studies. This new NDL^UCD cell line model is a practical alternative to the more commonly used 4T1 cells, and our previously described FVB/N-Tg(MMTV-PyVT)634Mul derived Met-1^fvb2 and FVB/NTg(MMTV-PyVT^Y315F/Y322F) derived DB-7^fvb2 cell lines. The NDL^UCD cells have, so far, remained genetically and phenotypically stable over many generations, with consistent and reproducible results in immune intact preclinical cohorts.

Combining activatable nanodelivery with immunotherapy in a murine breast cancer model

A successful chemotherapy-immunotherapy solid-tumor protocol should accomplish the following goals: debulk large tumors, release tumor antigen for cross-presentation and cross-priming, release cancer-suppressive cytokines and enhance anti-tumor immune cell populations. Thermally-activated drug delivery particles have the potential to synergize with immunotherapeutics to accomplish these goals; activation can release chemotherapy within bulky solid tumors and can enhance response when combined with immunotherapy. We set out to determine whether a single protocol, combining locally-activated chemotherapy and agonist immunotherapy, could accomplish these goals and yield a potentially translational therapy. For effective delivery of free doxorubicin to tumors with minimal toxicity, we stabilized doxorubicin with copper in temperature-sensitive liposomes that rapidly release free drug in the vasculature of cancer lesions upon exposure to ultrasound-mediated hyperthermia. We found that in vitro exposure of tumor cells to hyperthermia and doxorubicin resulted in immunogenic cell death and the local release of type I interferons across murine cancer cell lines. Following intravenous injection, local activation of the liposomes within a single tumor released doxorubicin and enhanced cross-presentation of a model antigen at distant tumor sites. While a variety of protocols achieved a complete response in >50% of treated mice, the complete response rate was greatest (90%) when 1 week of immunotherapy priming preceded a single activatable chemotherapeutic administration. While repeated chemotherapeutic delivery reduced local viable tumor, the complete response rate and a subset of tumor immune cells were also reduced. Taken together, the results suggest that activatable chemotherapy can enhance adjuvant immunotherapy; however, in a murine model the systemic adaptive immune response was greatest with a single administration of chemotherapy.

Unimicellar hyperstars as multi-antigen cancer nanovaccines displaying clustered epitopes of immunostimulating peptides

Unimicellar hyperstar macromolecular chimeras displaying multiple melanoma peptide antigens were prepared primarily via a combination of click chemistry and esterification reactions starting from a biodegradable hyperbranched polymer template. Solubilization of the hyperstars in aqueous solution afforded a multi-antigen unimicellar cancer nanovaccine of about 20 nm. The nanovaccine showed good biocompatibility and uptake by dendritic cells in vitro. An in vivo evaluation of the nanovaccine therapeutic efficacy against melanoma in mice implanted with B16OVA tumors revealed significantly greater T-cell recruitment and improved survival rates for mice treated with nanovaccine and adjuvant compared to non-treated mice.

CD8+ T-Cell Density Imaging with 64Cu-Labeled Cys-Diabody Informs Immunotherapy Protocols

Purpose: Noninvasive and quantitative tracking of CD8⁺ T cells by PET has emerged as a potential technique to gauge response to immunotherapy. We apply an anti-CD8 cys-diabody, labeled with ⁶⁴Cu, to assess the sensitivity of PET imaging of normal and diseased tissue.Experimental Design: Radiolabeling of an anti-CD8 cys-diabody (169cDb) with ⁶⁴Cu was developed. The accumulation of ⁶⁴Cu-169cDb was evaluated with PET/CT imaging (0, 5, and 24 hours) and biodistribution (24 hours) in wild-type mouse strains (n = 8/group studied with imaging and IHC or flow cytometry) after intravenous administration. Tumor-infiltrating CD8⁺ T cells in tumor-bearing mice treated with CpG and αPD-1 were quantified and mapped (n = 6-8/group studied with imaging and IHC or flow cytometry).Results: We demonstrate the ability of immunoPET to detect small differences in CD8⁺ T-cell distribution between mouse strains and across lymphoid tissues, including the intestinal tract of normal mice. In FVB mice bearing a syngeneic HER2-driven model of mammary adenocarcinoma (NDL), ⁶⁴Cu-169cDb PET imaging accurately visualized and quantified changes in tumor-infiltrating CD8⁺ T cells in response to immunotherapy. A reduction in the circulation time of the imaging probe followed the development of treatment-related liver and splenic hypertrophy and provided an indication of off-target effects associated with immunotherapy protocols.Conclusions: ⁶⁴Cu-169cDb imaging can spatially map the distribution of CD8⁺ T cells in normal organs and tumors. ImmunoPET imaging of tumor-infiltrating cytotoxic CD8⁺ T cells detected changes in T-cell density resulting from adjuvant and checkpoint immunotherapy protocols in our preclinical evaluation. Clin Cancer Res; 24(20); 4976-87. ©2018 AACR.

Distinct immune signatures in directly treated and distant tumors result from TLR adjuvants and focal ablation

Both adjuvants and focal ablation can alter the local innate immune system and trigger a highly effective systemic response. Our goal is to determine the impact of these treatments on directly treated and distant disease and the mechanisms for the enhanced response obtained by combinatorial treatments.

Methods: We combined RNA-sequencing, flow cytometry and TCR-sequencing to dissect the impact of immunotherapy and of immunotherapy combined with ablation on local and systemic immune components.

Results: With administration of a toll-like receptor agonist agonist (CpG) alone or CpG combined with same-site ablation, we found dramatic differences between the local and distant tumor environments, where the directly treated tumors were skewed to high expression of F4/80, Cd11b and Tnf and the distant tumors to enhanced Cd11c, Cd3 and Ifng. When ablation was added to immunotherapy, 100% (n=20/20) of directly treated tumors and 90% (n=18/20) of distant tumors were responsive. Comparing the combined ablation-immunotherapy treatment to immunotherapy alone, we find three major mechanistic differences. First, while ablation alone enhanced intratumoral antigen cross-presentation (up to ~8% of CD45⁺ cells), systemic cross-presentation of tumor antigen remained low. Combining same-site ablation with CpG amplified cross-presentation in the draining lymph node (~16% of CD45⁺ cells) compared to the ablation-only (~0.1% of CD45⁺ cells) and immunotherapy-only cohorts (~10% of CD45⁺ cells). Macrophages and DCs process and present this antigen to CD8⁺ T-cells, increasing the number of unique T-cell receptor rearrangements in distant tumors. Second, type I interferon (IFN) release from tumor cells increased with the ablation-immunotherapy treatment as compared with ablation or immunotherapy alone. Type I IFN release is synergistic with toll-like receptor activation in enhancing cytokine and chemokine expression. Expression of genes associated with T-cell activation and stimulation (Eomes, Prf1 and Icos) was 27, 56 and 89-fold higher with ablation-immunotherapy treatment as compared to the no-treatment controls (and 12, 32 and 60-fold higher for immunotherapy-only treatment as compared to the no-treatment controls). Third, we found that the ablation-immunotherapy treatment polarized macrophages and dendritic cells towards a CD169 subset systemically, where CD169⁺ macrophages are an IFN-enhanced subpopulation associated with dead-cell antigen presentation.

Conclusion: While the local and distant responses are distinct, CpG combined with ablative focal therapy drives a highly effective systemic immune response.

Toward Personalized Peptide-Based Cancer Nanovaccines: A Facile and Versatile Synthetic Approach

Personalized cancer vaccines (PCVs) are receiving attention as an avenue for cancer immunotherapy. PCVs employ immunogenic peptide epitopes capable of stimulating the immune system to destroy cancer cells with great specificity. Challenges associated with effective delivery of these peptides include poor solubility of hydrophobic sequences, rapid clearance, and poor immunogenicity, among others. The incorporation of peptides into nanoparticles has the potential to overcome these challenges, but the broad range of functionalities found in amino acids presents a challenge to conjugation due to possible interferences and lack of reaction specificity. Herein, a facile and versatile approach to generating nanosized PCVs under mild nonstringent conditions is reported. Following a simple two-step semibatch synthetic approach, amphiphilic hyperbranched polymer-peptide conjugates were prepared by the conjugation of melanoma antigen peptides, either TRP2 (hydrophobic) or MUT30 (hydrophilic), to an alkyne functionalized core via strain-promoted azide-alkyne click chemistry. Self-assembly of the amphiphiles gave spherical nanovaccines (by transmission electron microscopy) with sizes in the range of 10-30 nm (by dynamic light scattering). Fluorescently labeled nanovaccines were prepared to investigate the cellular uptake by antigen presenting cells (dendritic cells), and uptake was confirmed by flow cytometry and microscopy. The TRP2 nanovaccine was taken up the most followed by MUT30 nanoparticles and, finally, nanoparticles without peptide. The nanovaccines showed good biocompatibility against B16-F10 cells, yet the TRP2 peptide showed signs of toxicity, possibly due to its hydrophobicity. A test for immunogenicity revealed that the nanovaccines were poorly immunogenic, implying the need for an adjuvant when administered in vivo. Treatment of mice with melanoma tumors showed that in combination with adjuvant, CpG, groups with the peptide nanovaccines slowed tumor growth and improved survival (up to 24 days, TRP2) compared to the untreated group (14 days).

Abstract 576: Neoadjuvant immunotherapy improves efficacy of image-guided thermal ablation to generate curative responses in a murine breast cancer model

Magnetic resonance-guided focused ultrasound (MRgFUS) facilitates local tumor control via thermal ablation, however, the anti-tumor immune effects induced are weak and unable to consistently generate robust objective responses in distant lesions. Here, we set out to optimize a therapeutic approach for employing immunotherapy with thermal ablation for systemic cancer treatment. We assessed the efficacy of implementing MRgFUS ablation with blockade of the PD-1/PD-L1 axis (anti-PD-1) and activation of TLR9 (CpG oligonucleotide) under various protocols and in multiple models of murine cancer. Anti-PD-1 (200 µg, i.p., days 21 & 28) and CpG (100 µg, i.t., days 21, 24 and 28) were administered coincidentally with MRgFUS ablation (3 MHz central frequency, circular pattern with R=2 mm, 1 revolution per second, 65ºC for 1 min, days 21 and 28) over the course of a week in bilateral syngeneic neu deletion line (NDL), 4T-1 and B16 tumor bearing mice. Additionally, we evaluated the administration of immunotherapy prior to a course of thermal ablation (i.e., “primed ablation”), where anti-PD-1 (as above on days 21, 28 & 35), CpG (as above on days 21, 24, 28, 31, 38 and 45) and MRgFUS ablation (as above on days 31, 38 and 45) were administered in bilateral NDL tumor-bearing mice. Primed ablation generated a robust anti-tumor immune response in distant lesions two weeks after the start of treatment, where a threefold increase in tumor infiltrating leukocytes (reaching 40% CD8+ and 20% CD4+ T-cells) was observed. This led to a complete response in 80% of treated mice within 70 days after treatment commenced. This effect was also observed in animals with high tumor burden and when thermal ablation was performed sequentially at multiple independent sites; 80% of untreated lesions were eradicated at 50 days after the start of treatment. However, therapeutic efficacy was limited when thermal ablation was performed coincident with the first dose of immunotherapy; this protocol was not curative in any murine model. To elucidate the mechanism for this effect, we employed tumor histology and positron emission tomography immediately after MRgFUS ablation. We found that thermal ablation induced stromal inflammation, and the loss of cell-cell adhesion and local vascular integrity, which impacted the intratumoral transport of small molecules and proteins for 48 hours post treatment. These data suggest that tumor debulking using image-guided thermal therapy can be successfully incorporated within a curative protocol in which immunotherapy is initiated before ablation.

Citation Format: Matthew T. Silvestrini, Elizabeth S. Ingham, Lisa M. Mahakian, Azadeh Kheirolomoom, Yu Liu, Brett Z. Fite, Sarah M. Tam, Samantha Tucci, Katherine D. Watson, Andrew W. Wong, Arta M. Monjazeb, Neil E. Hubbard, William J. Murphy, Alexander D. Borowsky, Katherine W. Ferrara. Neoadjuvant immunotherapy improves efficacy of image-guided thermal ablation to generate curative responses in a murine breast cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 576. doi:10.1158/1538-7445.AM2017-576

Priming is key to effective incorporation of image-guided thermal ablation into immunotherapy protocols

Focal therapies play an important role in the treatment of cancers where palliation is desired, local control is needed, or surgical resection is not feasible. Pairing immunotherapy with such focal treatments is particularly attractive; however, there is emerging evidence that focal therapy can have a positive or negative impact on the efficacy of immunotherapy. Thermal ablation is an appealing modality to pair with such protocols, as tumors can be rapidly debulked (cell death occurring within minutes to hours), tumor antigens can be released locally, and treatment can be conducted and repeated without the concerns of radiation-based therapies. In a syngeneic model of epithelial cancer, we found that 7 days of immunotherapy (TLR9 agonist and checkpoint blockade), prior to thermal ablation, reduced macrophages and myeloid-derived suppressor cells and enhanced IFN-γ-producing CD8⁺ T cells, the M1 macrophage fraction, and PD-L1 expression on CD45⁺ cells. Continued treatment with immunotherapy alone or with immunotherapy combined with ablation (primed ablation) then resulted in a complete response in 80% of treated mice at day 90, and primed ablation expanded CD8⁺ T cells as compared with all control groups. When the tumor burden was increased by implantation of 3 orthotopic tumors, successive primed ablation of 2 discrete lesions resulted in survival of 60% of treated mice as compared with 25% of mice treated with immunotherapy alone. Alternatively, when immunotherapy was begun immediately after thermal ablation, the abscopal effect was diminished and none of the mice within the cohort exhibited a complete response. In summary, we found that immunotherapy begun before ablation can be curative and can enhance efficacy in the presence of a high tumor burden. Two mechanisms have potential to impact the efficacy of immunotherapy when begun immediately after thermal ablation: mechanical changes in the tumor microenvironment and inflammatory-mediated changes in immune phenotype.

Abstract LB-052: Activatable nanodelivery combined with CpG-ODN and anti-PD-1 achieves a complete response in directly-treated and contralateral tumors in a murine breast cancer model

We demonstrate for the first time that blocking of the programmed death-1 (PD-1) pathway in conjunction with immunogenic cell death induced by CpG-ODN and activatable nanodelivery of doxorubicin can generate curative responses in both primary and contralateral tumors. Activatable nanotherapeutics are attractive since the toxicity of chemotherapeutics can be constrained to a small region; combining such a strategy with immunotherapy is the goal of this study. We have previously shown that administration of CpG-ODN as an adjuvant, together with local release of doxorubicin from temperature sensitive liposomes (TSL) resulted in regression of directly-treated tumors, suppressed growth of contralateral tumors and reduced chemotherapeutic-mediated toxicity in a murine breast cancer model.1 Increases in cytotoxic CD8+ T lymphocytes and a reduction in regulatory T cells and myeloid-derived suppressor cells were observed in both directly treated and contralateral tumors. This combinatorial approach was curative for directly-treated tumors and overall survival was significantly extended, however, the contralateral tumor returned in all treated mice. The following is the protocol explored for the addition of anti-PD1: immune intact FVB/n mice with bilateral invasive neu deletion syngeneic transplanted tumors were treated with a combination of anti-PD1 (aPD-1, 200 μg, i.p.) and intratumoral administration of CpG-ODN (100 μg, i.t.) on days 0, 7, 14 and 0, 3, 7, 10, 17 and 24, respectively. Doxorubicin TSL were prepared from DPPC:MPPC:DSPE-PEG2k, 86:10:4 in the presence of copper (II) gluconate and triethanolamine at 0.2 mg-drug/mg-lipid and administrated i.v. at 6 mg doxorubicin/kg body weight on days 10, 17, 24. The formation of a complex between doxorubicin and copper was created to enhance the circulation and stability of TSL and to reduce systemic toxicity. To trigger drug release, hyperthermia was induced in the primary tumor with ultrasound (peak ultrasound pressure of 1.1 MPa at a frequency of 1.5 MHz) at 42°C for 5 min prior to and 20 min post drug injection with a variable duty cycle. Immediately afterwards, 100 μg of CpG-ODN 1826 was administered intratumorally to the insonified tumor. Upon treatment with this combination of locally-released doxorubicin, local administration of CpG-ODN and systemic aPD-1, 100% of treated and contralateral tumors regressed by at least 80%; further, all of the directly-treated tumors and 50% of the contralateral tumors were eliminated without recurrence. Thus, a 50% complete response rate was achieved, with tumor regression observed immediately after the incorporation of the doxorubicin treatment. By contrast, administration of CpG-ODN and systemic aPD-1 alone resulted in regression of 66% of treated and contralateral tumors.

*MS and AK contributed equally to this work.

1. J Control Release (2015); 220: 253-264.

Citation Format: Matthew T. Silvestrini, Azadeh Kheirolomoom, Elizabeth S. Ingham, Lisa M. Mahakian, Sarah M. Tam, Josquin Foiret, Samantha Tucci, Neil E. Hubbard, Alexander D. Borowsky, Katherine W. Ferrara. Activatable nanodelivery combined with CpG-ODN and anti-PD-1 achieves a complete response in directly-treated and contralateral tumors in a murine breast cancer model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-052.

CpG expedites regression of local and systemic tumors when combined with activatable nanodelivery

Ultrasonic activation of nanoparticles provides the opportunity to deliver a large fraction of the injected dose to insonified tumors and produce a complete local response. Here, we evaluate whether the local and systemic response to chemotherapy can be enhanced by combining such a therapy with locally-administered CpG as an immune adjuvant. In order to create stable, activatable particles, a complex between copper and doxorubicin (CuDox) was created within temperature-sensitive liposomes. Whereas insonation of the CuDox liposomes alone has been shown to produce a complete response in murine breast cancer after 8 treatments of 6 mg/kg delivered over 4 weeks, combining this treatment with CpG resolved local cancers within 3 treatments delivered over 7 days. Further, contralateral tumors regressed as a result of the combined treatment, and survival was extended in systemic disease. In both the treated and contralateral tumor site, the combined treatment increased leukocytes and CD4+ and CD8+ T-effector cells and reduced myeloid-derived suppressor cells (MDSCs). Taken together, the results suggest that this combinatorial treatment significantly enhances the systemic efficacy of locally-activated nanotherapy.

Interventional magnetic resonance imaging-guided cell transplantation into the brain with radially branched deployment

Intracerebral cell transplantation is being pursued as a treatment for many neurological diseases, and effective cell delivery is critical for clinical success. To facilitate intracerebral cell transplantation at the scale and complexity of the human brain, we developed a platform technology that enables radially branched deployment (RBD) of cells to multiple target locations at variable radial distances and depths along the initial brain penetration tract with real-time interventional magnetic resonance image (iMRI) guidance. iMRI-guided RBD functioned as an "add-on" to standard neurosurgical and imaging workflows, and procedures were performed in a commonly available clinical MRI scanner. Multiple deposits of super paramagnetic iron oxide beads were safely delivered to the striatum of live swine, and distribution to the entire putamen was achieved via a single cannula insertion in human cadaveric heads. Human embryonic stem cell-derived dopaminergic neurons were biocompatible with the iMRI-guided RBD platform and successfully delivered with iMRI guidance into the swine striatum. Thus, iMRI-guided RBD overcomes some of the technical limitations inherent to the use of straight cannulas and standard stereotactic targeting. This platform technology could have a major impact on the clinical translation of a wide range of cell therapeutics for the treatment of many neurological diseases.

Devices for cell transplantation into the central nervous system: Design considerations and emerging technologies

Successful use of cell-based therapies for the treatment of neurological diseases is dependent upon effective delivery to the central nervous system (CNS). The CNS poses several challenges to the delivery of cell-based therapeutics, including the blood-brain barrier, anatomic complexity, and regional specificity. Targeted delivery methods are therefore required for the selective treatment of specific CNS regions. In addition, CNS tissues are mechanically and physiologically delicate and even minor injury to normal brain or spinal cord can cause devastating neurological deficits. Targeted delivery methods must therefore minimize tissue trauma. At present, direct injection into brain or spinal cord parenchyma promises to be the most versatile and accurate method of targeted CNS therapeutic delivery. While direct injection methods have already been employed in clinical trials of cell transplantation for a wide variety of neurological diseases, there are many shortcomings with the devices and surgical approaches currently used. Some of these technical limitations may hinder the clinical development of cell transplantation therapies despite validity of the underlying biological mechanisms. In this review, we discuss some of the important technical considerations of CNS injection devices such as targeting accuracy, distribution of infused therapeutic, and overall safety to the patient. We also introduce and discuss an emerging technology - radially branched deployment - that may improve our ability to safely distribute cell-based therapies and other therapeutic agents to the CNS. Finally, we speculate on future technological developments that may further enhance the efficacy of CNS therapeutic delivery.

Radially branched deployment for more efficient cell transplantation at the scale of the human brain

BACKGROUND

In preclinical studies, cell transplantation into the brain has shown great promise for the treatment of a wide range of neurological diseases. However, the use of a straight cannula and syringe for cell delivery to the human brain does not approximate cell distribution achieved in animal studies. This technical deficiency may limit the successful clinical translation of cell transplantation.

OBJECTIVE

To develop a stereotactic device that effectively distributes viable cells to the human brain. Our primary aims were to (1) minimize the number of transcortical penetrations required for transplantation, (2) reduce variability in cell dosing and (3) increase cell survival.

METHODS

We developed a modular cannula system capable of radially branched deployment (RBD) of a cell delivery catheter at variable angles from the longitudinal device axis. We also developed an integrated catheter-plunger system, eliminating the need for a separate syringe delivery mechanism. The RBD prototype was evaluated in vitro and in vivo with subcortical injections into the swine brain. Performance was compared to a 20G straight cannula with dual side ports, a device used in current clinical trials.

RESULTS

RBD enabled therapeutic delivery in a precise 'tree-like' pattern branched from a single initial trajectory, thereby facilitating delivery to a volumetrically large target region. RBD could transplant materials in a radial pattern up to 2.0 cm from the initial penetration tract. The novel integrated catheter-plunger system facilitated manual delivery of small and precise volumes of injection (1.36 ± 0.13 µl per cm of plunger travel). Both dilute and highly concentrated neural precursor cell populations tolerated transit through the device with high viability and unaffected developmental potential. While reflux of infusate along the penetration tract was problematic with the use of the 20G cannula, RBD was resistant to this source of cell dose variability in agarose. RBD enabled radial injections to the swine brain when used with a modern clinical stereotactic system.

CONCLUSIONS

By increasing the total delivery volume through a single transcortical penetration in agarose models, RBD strategy may provide a new approach for cell transplantation to the human brain. Incorporation of RBD or selected aspects of its design into future clinical trials may increase the likelihood of successful translation of cell-based therapy to the human patient.

Nanoengineered surfaces enhance drug loading and adhesion

To circumvent the barriers encountered by macromolecules at the gastrointestinal mucosa, sufficient therapeutic macromolecules must be delivered in close proximity to cells.(1) Previously, we have shown that silicon nanowires penetrate the mucous layer and adhere directly to cells under high shear.(2) In this work, we characterize potential reservoirs and load macromolecules into interstitial space between nanowires. We show significant increases in loading capacity due to nanowires while retaining adhesion of loaded particles under high shear.