Proteomic analysis reveals mechanisms underlying increased efficacy of bleomycin by photochemical internalization in bladder cancer cells

Photochemical internalization (PCI) is a promising new technology for site-specific drug delivery, developed from photodynamic therapy (PDT). In PCI, light-induced activation of a photosensitizer trapped inside endosomes together with e.g. chemotherapeutics, nucleic acids or immunotoxins, allows cytosolic delivery and enhanced local therapeutic effect. Here we have evaluated the photosensitizer meso-tetraphenyl chlorine disulphonate (TPCS2a/fimaporfin) in a proteome analysis of AY-27 rat bladder cancer cells in combination with the chemotherapeutic drug bleomycin (BML). We find that BLMPCI attenuates oxidative stress responses induced by BLM alone, while concomitantly increasing transcriptional repression and DNA damage responses. BLMPCI also mediates downregulation of bleomycin hydrolase (Blmh), which is responsible for cellular degradation of BLM, as well as several factors known to be involved in fibrotic responses. PCI-mediated delivery might thus allow reduced dosage of BLM and alleviate unwanted side effects from treatment, including pulmonary fibrosis.

Photochemically-Mediated Inflammation and Cross-Presentation of Mycobacterium bovis BCG Proteins Stimulates Strong CD4 and CD8 T-Cell Responses in Mice

Conventional vaccines are very efficient in the prevention of bacterial infections caused by extracellular pathogens due to effective stimulation of pathogen-specific antibodies. In contrast, considering that intracellular surveillance by antibodies is not possible, they are typically less effective in preventing or treating infections caused by intracellular pathogens such as Mycobacterium tuberculosis. The objective of the current study was to use so-called photochemical internalization (PCI) to deliver a live bacterial vaccine to the cytosol of antigen-presenting cells (APCs) for the purpose of stimulating major histocompatibility complex (MHC) I-restricted CD8 T-cell responses. For this purpose, Mycobacterium bovis BCG (BCG) was combined with the photosensitiser tetraphenyl chlorine disulfonate (TPCS2a) and injected intradermally into mice. TPCS2a was then activated by illumination of the injection site with light of defined energy. Antigen-specific CD4 and CD8 T-cell responses were monitored in blood, spleen, and lymph nodes at different time points thereafter using flow cytometry, ELISA and ELISPOT. Finally, APCs were infected and PCI-treated in vitro for analysis of their activation of T cells in vitro or in vivo after autologous vaccination of mice. Combination of BCG with PCI induced stronger BCG-specific CD4 and CD8 T-cell responses than treatment with BCG only or with BCG and TPCS2a without light. The overall T-cell responses were multifunctional as characterized by the production of IFN-γ, TNF-α, IL-2 and IL-17. Importantly, PCI induced cross-presentation of BCG proteins for stimulation of antigen-specific CD8 T-cells that were particularly producing IFN-γ and TNF-α. PCI further facilitated antigen presentation by causing up-regulation of MHC and co-stimulatory proteins on the surface of APCs as well as their production of TNF-α and IL-1β in vivo. Furthermore, PCI-based vaccination also caused local inflammation at the site of vaccination, showing strong infiltration of immune cells, which could contribute to the stimulation of antigen-specific immune responses. This study is the first to demonstrate that a live microbial vaccine can be combined with a photochemical compound and light for cross presentation of antigens to CD8 T cells. Moreover, the results revealed that PCI treatment strongly improved the immunogenicity of M. bovis BCG.

OUP accepted manuscript

Background

Photochemical internalization (PCI) is a novel technology for light-induced enhancement of the local therapeutic effect of cancer drugs, utilizing a specially designed photosensitizing molecule (fimaporfin). The photosensitizing molecules are trapped in endosomes along with macromolecules or drugs. Photoactivation of fimaporfin disrupts the endosomal membranes so that drug molecules are released from endosomes inside cells and can reach their therapeutic target in the cell cytosol or nucleus. Compared with photodynamic therapy, the main cytotoxic effect with PCI is disruption of the endosomal membrane resulting in delivery of chemotherapy drug, and not to the photochemical reactions per se. In this study we investigated the effect of PCI with gemcitabine in patients with inoperable perihilar cholangiocarcinoma (CCA).

Methods

The in vitro cytotoxic effect of PCI with gemcitabine was studied on two CCA-derived cell lines. In a fimaporfin dose-escalation phase I clinical study, we administered PCI with gemcitabine in patients with perihilar CCA (n = 16) to establish a safe and tolerable fimaporfin dose and to get early signals of efficacy. The patients enrolled in the study had tumors in which the whole length of the tumor could be illuminated from the inside of the bile duct, using an optical fiber inserted via an endoscope (Fig. 1). Fimaporfin was administered intravenously at day 0; gemcitabine (i.v.) and intraluminal biliary endoscopic laser light application on day 4; followed by standard gemcitabine/cisplatin chemotherapy.

Results

Preclinical experiments showed that PCI enhanced the effect of gemcitabine. In patients with CCA, PCI with gemcitabine was well tolerated with no dose-limiting toxicities, and no unexpected safety signals. Disease control was achieved in 10 of 11 evaluable patients, with a clearly superior effect in the two highest dose groups. The objective response rate (ORR) was 42%, including two complete responses, while ORR at the highest dose was 60%. Progression-free survival at 6 months was 75%, and median overall survival (mOS) was 15.4 months, with 22.8 months at the highest fimaporfin dose.

Conclusion

Photochemical internalization with gemcitabine was found to be safe and resulted in encouraging response and survival rates in patients with unresectable perihilar CCA.

Squamous cell carcinoma of the ear treated by photochemical internalization

A 77-year-old Caucasian male was diagnosed with squamous cell cancer of the right ear. The patient elected to take part in the first-in-man phase I TPCS_2a based bleomycin photochemical internalization (PCI). On Day 0, The patient received the photosensitiser [Amphinex (TPCS_2a)], by slow intravenous injection. Four days later, surface illumination based (PCI) was implemented 3 h after the slow infusion of Bleomycin. Four weeks following the infusion of the photosensitiser, the cancerous area turned into black rigid mass with clear demarcation from the macroscopically normal skin. The size of the treated area has been substantially reduced. Histopathologic assessment of the excised necrotic mass revealed no viable tumour and the excised margins (PCI-treated margins) were tumour-free. This case was a clear indication that PCI is a clinically relevant technique that has potential in the treatment of such cancers to avoid radical intervention.

Photochemical internalization (PCI)-mediated activation of CD8 T cells involves antigen uptake and CCR7-mediated transport by migratory dendritic cells to draining lymph nodes

Antigen cross-presentation to cytotoxic CD8⁺ T cells is crucial for the induction of anti-tumor and anti-viral immune responses. Recently, co-encapsulation of photosensitizers and antigens into microspheres and subsequent photochemical internalization (PCI) of antigens in antigen presenting cells has emerged as a promising new strategy for inducing antigen-specific CD8⁺ T cell responses in vitro and in vivo. However, the exact cellular mechanisms have hardly been investigated in vivo, i.e., which cell types take up antigen-loaded microspheres at the site of injection, or in which secondary lymphoid organ does T cell priming occur? We used spray-dried poly(lactic-co-glycolic acid) (PLGA) microspheres loaded with ovalbumin and the photosensitizer tetraphenyl chlorine disulfonate (TPCS_2a) to investigate these processes in vivo. Intravital microscopy and flow cytometric analysis of the murine ear skin revealed that dendritic cells (DCs) take up PLGA microspheres in peripheral tissues. Illumination then caused photoactivation of TPCS_2a and induced local tissue inflammation that enhanced CCR7-dependent migration of microsphere-containing DCs to tissue-draining lymph nodes (LNs), i.e., the site of CD8⁺ T cell priming. The results contribute to a better understanding of the functional mechanism of PCI-mediated vaccination and highlight the importance of an active transport of vaccine microspheres by antigen presenting cells to draining LNs.

Photochemical Internalization Enhanced Vaccination Is Safe, and Gives Promising Cellular Immune Responses to an HPV Peptide-Based Vaccine in a Phase I Clinical Study in Healthy Volunteers

Background and Aims

Photochemical internalization (PCI) is a technology for inducing release of endocytosed antigens into the cell cytosol via a light-induced process. Preclinical experiments have shown that PCI improves MHC class I antigen presentation, resulting in strongly enhanced CD8+ T-cell responses to polypeptide antigens. In PCI vaccination a mixture of the photosensitizing compound fimaporfin, vaccine antigens, and an adjuvant is administered intradermally followed by illumination of the vaccination site. This work describes an open label, phase I study in healthy volunteers, to assess the safety, tolerability, and immune response to PCI vaccination in combination with the adjuvant poly-ICLC (Hiltonol) (ClinicalTrials.gov Identifier: NCT02947854).

Methods

The primary objective of the study was to assess the safety and local tolerance of PCI mediated vaccination, and to identify a safe fimaporfin dose for later clinical studies. A secondary objective was to analyze the immunological responses to the vaccination. Each subject received 3 doses of HPV16 E7 peptide antigens and two doses of Keyhole Limpet Hemocyanin (KLH) protein. A control group received Hiltonol and vaccine antigens only, whereas the PCI groups in addition received fimaporfin + light. Local and systemic adverse effects were assessed by standard criteria, and cellular and humoral immune responses were analyzed by ELISpot, flow cytometry, and ELISA assays.

Results

96 healthy volunteers were vaccinated with fimaporfin doses of 0.75–50 µg. Doses below 17.5 µg were safe and tolerable, higher doses exhibited local tolerability issues in some study subjects, mainly erythema, and pain during illumination. There were few, and only mild and expected systemic adverse events. The employment of PCI increased the number of subjects exhibiting a T-cell response to the HPV peptide vaccine about 10-fold over what was achieved with the antigen/Hiltonol combination without PCI. Moreover, the use of PCI seemed to result in a more consistent and multifunctional CD8+ T-cell response. An enhancement of the humoral immune response to KLH vaccination was also observed.

Conclusions

Using PCI in combination with Hiltonol for intradermal vaccination is safe at fimaporfin doses below 17.5 µg, and gives encouraging immune responses to peptide and protein based vaccination.

Drug-Loaded Photosensitizer-Chitosan Nanoparticles for Combinatorial Chemo- and Photodynamic-Therapy of Cancer

In this study we have developed biodegradable polymeric nanoparticles (NPs) containing the cytostatic drugs mertansine (MRT) or cabazitaxel (CBZ). The NPs are based on chitosan (CS) conjugate polymers synthesized with different amounts of the photosensitizer tetraphenylchlorin (TPC). These TPC–CS NPs have high loading capacity and strong drug retention due to π–π stacking interactions between the drugs and the aromatic photosensitizer groups of the polymers. CS polymers with 10% of the side chains containing TPC were found to be optimal in terms of drug loading capacity and NP stability. The TPC–CS NPs loaded with MRT or CBZ displayed higher cytotoxicity than the free form of these drugs in the breast cancer cell lines MDA-MB-231 and MDA-MB-468. Furthermore, light-induced photochemical activation of the NPs elicited a strong photodynamic therapy effect on these breast cancer cells. Biodistribution studies in mice showed that most of the TPC–CS NPs accumulated in liver and lungs, but they were also found to be localized in tumors derived from HCT-116 cells. These data suggest that the drug-loaded TPC–CS NPs have a potential in combinatory anticancer therapy and as contrast agents.

Apparent Complete Response of a Treatment Refractory and Recurrent Squamous Cell Carcinoma Lesion to Photochemical Internalization: A Clinical Case Study

Photochemical internalization (PCI) depends on the delivery of sublethal photodynamic reaction to facilitate the work of a chemotherapeutic agent. We discuss our experience in managing a patient with extensive squamous cell carcinoma of the right face and scalp under the TPCS_2a -based bleomycin PCI treatment protocol. In this case, an 84-year-old Caucasian received 0.25 mg kg^-1 of TPCS_2a (Amphinex^® , PCI Biotech AS, Oslo, Norway). Surface illumination photochemical internalization was carried out after 4 days, which was preceded by the chemotherapeutic agent infusion (Bleomycin). After one week from the illumination time, tissue necrosis was evident and tumor shrinkage was most noticeable at day 14 postillumination. Follow-up at 6 weeks continued to show tissue healing and regeneration with no clinical evidence of recurrence. Multiple surgical biopsies were taken at 1 and 3 months postillumination and found to be tumor free. PCI's depth of effect has been very significant with negligible damage to the collateral tissues. This technology has a role in interventional oncology especially when managing challenging cases.

Combined Photosensitization and Vaccination Enable CD8 T-Cell Immunity and Tumor Suppression Independent of CD4 T-Cell Help

Cytotoxic T lymphocytes (CTLs) are key players in fighting cancer, and their induction is a major focus in the design of therapeutic vaccines. Yet, therapeutic vaccine efficacy is limited, in part due to the suboptimal vaccine processing by antigen-presenting cells (APCs). Such processing typically takes place via the MHC class II pathway for CD4 T-cell activation and MHC class I pathway for activation of CD8 CTLs. We show that a combination of skin photochemical treatment and immunization, so-called photochemical internalization (PCI) facilitated CTL activation due to the photochemical adjuvant effect induced by photosensitizer, oxygen, and light. Mice were immunized intradermally with antigen and photosensitizer, followed by controlled light exposure. PCI-treated mice showed strong activation of CD8 T cells, with improved IFN-γ production and cytotoxicity, as compared to mice immunized without parallel PCI treatment. Surprisingly, the CD8 T-cell effector functions were not impaired in MHC class II- or CD4 T-cell-deficient mice. Moreover, PCI-based vaccination caused tumor regression independent of MHC class II or CD4 T cells presence in melanoma bearing mice. Together, the data demonstrate that PCI can act as a powerful adjuvant in cancer vaccines, even in hosts with impaired T-helper functions.

Enhanced targeting of triple-negative breast carcinoma and malignant melanoma by photochemical internalization of CSPG4-targeting immunotoxins

Triple-negative breast cancer (TNBC) and malignant melanoma are highly aggressive cancers that widely express the cell surface chondroitin sulfate proteoglycan 4 (CSPG4/NG2). CSPG4 plays an important role in tumor cell growth and survival and promotes chemo- and radiotherapy resistance, suggesting that CSPG4 is an attractive target in cancer therapy. In the present work, we applied the drug delivery technology photochemical internalization (PCI) in combination with the novel CSPG4-targeting immunotoxin 225.28-saporin as an efficient and specific strategy to kill aggressive TNBC and amelanotic melanoma cells. Light-activation of the clinically relevant photosensitizer TPCS2a (fimaporfin) and 225.28-saporin was found to act in a synergistic manner, and was superior to both PCI of saporin and PCI-no-drug (TPCS2a + light only) in three TNBC cell lines (MDA-MB-231, MDA-MB-435 and SUM149) and two BRAFV600E mutated malignant melanoma cell lines (Melmet 1 and Melmet 5). The cytotoxic effect was highly dependent on the light dose and expression of CSPG4 since no enhanced cytotoxicity of PCI of 225.28-saporin compared to PCI of saporin was observed in the CSPG4-negative MCF-7 cells. The PCI of a smaller, and clinically relevant CSPG4-targeting toxin (scFvMEL-rGel) validated the CSPG4-targeting concept in vitro and induced a strong inhibition of tumor growth in the amelanotic melanoma xenograft A-375 model. In conclusion, the combination of the drug delivery technology PCI and CSPG4-targeting immunotoxins is an efficient, specific and light-controlled strategy for the elimination of aggressive cells of TNBC and malignant melanoma origin. This study lays the foundation for further preclinical evaluation of PCI in combination with CSPG4-targeting.

Photochemical internalization in bladder cancer - development of an orthotopic in vivo model

The possibility of using photochemical internalization (PCI) to enhance the effects of the cytotoxic drug bleomycin is investigated, together with photophysical determination and outlines of a possible treatment for intravesical therapy of bladder cancer. In vitro experiments indicated that the employment of PCI technology using the novel photosensitizer TPCS_2a® can enhance the cytotoxic effect of bleomycin in bladder cancer cells. Furthermore, experiments in an orthotopic in vivo bladder cancer model show an effective reduction in both the necrotic area and the bladder weight after TPCS_2a based photodynamic therapy (PDT). The tumor selectivity and PDT effects may be sufficient to destroy tumors without damaging the detrusor muscle layer. Our results present a possible new treatment strategy for non-muscle invasive bladder cancer, with the intravesical instillation of the photosensitizer and bleomycin followed by illumination through an optic fiber by using a catheter.

Photochemical Internalization of Peptide Antigens Provides a Novel Strategy to Realize Therapeutic Cancer Vaccination

Effective priming and activation of tumor-specific CD8+ cytotoxic T lymphocytes (CTLs) is crucial for realizing the potential of therapeutic cancer vaccination. This requires cytosolic antigens that feed into the MHC class I presentation pathway, which is not efficiently achieved with most current vaccination technologies. Photochemical internalization (PCI) provides an emerging technology to route endocytosed material to the cytosol of cells, based on light-induced disruption of endosomal membranes using a photosensitizing compound. Here, we investigated the potential of PCI as a novel, minimally invasive, and well-tolerated vaccination technology to induce priming of cancer-specific CTL responses to peptide antigens. We show that PCI effectively promotes delivery of peptide antigens to the cytosol of antigen-presenting cells (APCs) in vitro. This resulted in a 30-fold increase in MHC class I/peptide complex formation and surface presentation, and a subsequent 30- to 100-fold more efficient activation of antigen-specific CTLs compared to using the peptide alone. The effect was found to be highly dependent on the dose of the PCI treatment, where optimal doses promoted maturation of immature dendritic cells, thus also providing an adjuvant effect. The effect of PCI was confirmed in vivo by the successful induction of antigen-specific CTL responses to cancer antigens in C57BL/6 mice following intradermal peptide vaccination using PCI technology. We thus show new and strong evidence that PCI technology holds great potential as a novel strategy for improving the outcome of peptide vaccines aimed at triggering cancer-specific CD8+ CTL responses.

5-FU resistant EMT-like pancreatic cancer cells are hypersensitive to photochemical internalization of the novel endoglin-targeting immunotoxin CD105-saporin

BACKGROUND

Development of resistance to 5-fluorouracil (5-FU) is a major problem in treatment of various cancers including pancreatic cancer. In this study, we reveal important resistance mechanisms and photochemical strategies to overcome 5-FU resistance in pancreatic adenocarcinoma.

METHODS

5-FU resistant (5-FUR), epithelial-to-mesenchymal-like sub-clones of the wild type pancreatic cancer cell line Panc03.27 were previously generated in our lab. We investigated the cytotoxic effect of the endosomal/lysosomal-localizing photosensitizer TPCS2a (fimaporfin) combined with light (photochemical treatment, PCT) using MTS viability assay, and used fluorescence microscopy to show localization of TPCS2a and to investigate the effect of photodamage of lysosomes. Flow cytometric analysis was performed to investigate uptake of photosensitizer and to assess intracellular ROS levels. Expression and localization of LAMP1 was assessed using RT-qPCR, western blotting, and structured illumination microscopy. MTS viability assay was used to assess the effect of combinations of 5-FU, chloroquine (CQ), and photochemical treatment. Expression of CD105 was investigated using RT-qPCR, western blotting, flow cytometry, and fluorescence microscopy, and co-localization of TPCS2a and anti-CD105-saporin was assessed using microscopy. Lastly, the MTS assay was used to investigate cytotoxic effects of photochemical internalization (PCI) of the anti-CD105-immunotoxin.

RESULTS

The 5-FUR cell lines display hypersensitivity to PCT, which was linked to increased uptake of TPCS2a, altered lysosomal distribution, lysosomal photodamage and increased expression of the lysosomal marker LAMP-1 in the 5-FUR cells. We show that inhibition of autophagy induced by either chloroquine or lysosomal photodamage increases the sensitivity to 5-FU in the resistant cells. The three 5-FUR sub-clones overexpress Endoglin (CD105). Treatment with the immunotoxin anti-CD105-saporin alone significantly reduced the viability of the CD105-expressing 5-FUR cells, whereas little effect was seen in the CD105-negative non-resistant parental cancer cell lines. Strikingly, using the intracellular drug delivery method photochemical internalization (PCI) by combining light-controlled activation of the TPCS2a with nanomolar levels of CD105-saporin resulted in strong cytotoxic effects in the 5-FUR cell population.

CONCLUSION

Our findings suggested that autophagy is an important resistance mechanism against the chemotherapeutic drug 5-FU in pancreatic cancer cells, and that inhibition of the autophagy process, either by CQ or lysosomal photodamage, can contribute to increased sensitivity to 5-FU. For the first time, we demonstrate the promise of PCI-based targeting of CD105 in site-specific elimination of 5-FU resistant pancreatic cancer cells in vitro. In conclusion, PCI-based targeting of CD105 may represent a potent anticancer strategy and should be further evaluated in pre-clinical models.

Highly efficient destruction of squamous carcinoma cells of the head and neck by photochemical internalization of Ranpirnase

INTRODUCTION

Photochemical Internalization is a novel drug delivery technology for cancer treatment based on the principle of Photodynamic Treatment. Using a photosensitizer that locates in endocytic vesicles membranes of tumor cells, Photochemical internalization enables cytosolic release of endocytosed antitumor agents in a site-specific manner. The purpose of the present in-vitro study was to explore whether Photochemical Internalization is able to enhance the efficacy of Ranpirnase, a cytotoxic amphibian ribonuclease, for eradication of squamous cell carcinoma of the head and neck.

METHODS

Cell viability was measured in 8 primary human cell lines of squamous cell carcinoma of the head and neck after treatment with Ranpirnase and Photochemical Internalization. For Photochemical Internalization the photosensitizer disulfonated tetraphenyl porphine was incubated with tumor cells followed by exposure to blue light (435 nm).

RESULTS

Our study demonstrates significant enhancement of antitumor activity of Ranpirnase by Photochemical Internalization. Treatment responses were heterogeneous between the primary cancer cell lines. Combining Photochemical Internalization with Ranpirnase resulted in 4.6 to 1,940-fold increased cytotoxicity when compared with the ribonuclease alone (P < 0.05).

CONCLUSION

Cytotoxicity of Ranpirnase can be markedly enhanced by Photochemical Internalization in squamous cell carcinoma of the head and neck.

Endosome Targeting meso-Tetraphenylchlorin-Chitosan Nanoconjugates for Photochemical Internalization

Four amphiphilic covalently linked meso-tetraphenylchlorin-chitosan nanoconjugates were synthesized and evaluated for use in photochemical internalization (PCI) in vitro and in vivo. The synthetic protocol for the preparation of two different hydrophobic chlorin photosensitizers, 5-(4-aminophenyl)-10,15,20-triphenylchlorin and 5-(4-carboxyphenyl)-10,15,20-triphenylchlorin, was optimized. These monofunctional photosensitizers were covalently attached to carrier chitosan via silyl-protected 3,6-di-O-tert-butyldimethylsilyl-chitosan (Di-TBDMS-chitosan) with 0.10 degree of substitution per glucosamine (DS). Hydrophilic moieties such as trimethylamine and/or 1-methylpiperazine were incorporated with 0.9 DS to give fully water-soluble conjugates after removal of the TBDMS groups. A dynamic light scattering (DLS) study confirmed the formation of nanoparticles with a 140-200 nm diameter. These nanoconjugates could be activated at 650 nm (red region) light, with a fluorescence quantum yield (Φ_F) of 0.43-0.45, and are thus suitable candidates for use in PCI. These nanoconjugates were taken up and localized in the endocytic vesicles of HCT116/LUC human colon carcinoma cells, and upon illumination they substantially enhanced plasmid DNA transfection. The nanoconjugates were also evaluated in preliminary in vivo experiments in tumor-bearing mice, showing that the nanoconjugates could induce a strong photodynamic therapy (PDT) and also PCI effects in treatment with bleomycin.

Abstract A008: Photochemical internalization: Light-induced enhancement of MHC Class I antigen presentation, giving strong enhancement of cytotoxic T-cell responses to vaccination

For cancer vaccination and immunotherapy it is essential to stimulate cytotoxic T-cells (CTLs) to recognize and kill the tumor cells. Priming of CTLs is generally mediated through MHC Class I antigen presentation by antigen presenting cells (APCs). Since the MHC class I presentation machinery is localised in the cytosol, MHC class I presentation typically requires cytosolic delivery of the antigen. Unfortunately, this is often difficult to achieve with exogenously added peptide or protein antigens, since such antigens are primarily taken up into endocytic vesicles, and then “by default” are routed for MHC Class II presentation. Photochemical internalisation (PCI) is a technology that can help solving this problem by inducing an illumination-mediated permeabilisation of the membranes of endocytic vesicles, thereby releasing endocytosed antigens into the cytosol. This is achieved by employing a photosensitising molecule that is designed to localise specifically in endocytic membranes. Upon illumination, the photosensitiser induces photochemical reactions that make the membranes leaky, thereby releasing endocytosed molecules into the cytosol. In vitro it has been shown that the use of PCI leads to strongly increases MHC Class I presentation APCs. In vivo PCI-mediated vaccination is performed by injecting a mixture of vaccine and photosensitiser intradermally, followed by illumination of the injection site; and with this regimen, PCI substantially enhances immune responses to various types of polypeptide- based antigens. Thus, with short peptide antigens enhancement of CD8+ T-cell responses of up to 100 times have been observed when PCI is used in combination with the poly(IC) adjuvant; with a strong synergy between PCI and the adjuvant. With an HPV long peptide and with several protein antigens in addition to the CD8+ T-cell response a significant stimulation of CD4+ T-cell responses can also be observed, and in some cases also an increase in antibody production. In vivo studies with therapeutic peptide antigen vaccination in a mouse model for HPV-induced cancer show that the use of PCI strongly enhances anti-tumor responses to the vaccine, both when the vaccination is performed intradermally and when intratumoral administration is employed. The TPCS2a photosensitiser used in PCI is cheap to produce, withstands autoclavation and is stable for several years at ambient temperatures. TPCS2a is currently in clinical development for enhancement of the effect of cytotoxic anti-cancer drugs, and it has been shown that TPCS2a can be administered safely to patients in much higher doses than what is needed for the use in immunotherapy. In conclusion, PCI has a completely new mechanism of action as a vaccination enhancement technology, representing a new and potent tool for stimulation of CTL and in some cases also other types of immune responses. Preparations for a clinical study with PCI-mediated vaccination is on-going.

Citation Format: Tone Otterhaug, Markus Haug, Gaute Brede, Monika Håkerud, Anne Grete Nedberg, Victoria Edwards, Pål Kristian Selbo, Pål Johansen, Øyvind Halaas, Anders Høgset. Photochemical internalization: Light-induced enhancement of MHC Class I antigen presentation, giving strong enhancement of cytotoxic T-cell responses to vaccination [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A008.

Disulfonated tetraphenyl chlorin (TPCS2a)-induced photochemical internalisation of bleomycin in patients with solid malignancies: a phase 1, dose-escalation, first-in-man trial

BACKGROUND

Photochemical internalisation, a novel minimally invasive treatment, has shown promising preclinical results in enhancing and site-directing the effect of anticancer drugs by illumination, which initiates localised chemotherapy release. We assessed the safety and tolerability of a newly developed photosensitiser, disulfonated tetraphenyl chlorin (TPCS2a), in mediating photochemical internalisation of bleomycin in patients with advanced and recurrent solid malignancies.

METHODS

In this phase 1, dose-escalation, first-in-man trial, we recruited patients (aged ≥18 to <85 years) with local recurrent, advanced, or metastatic cutaneous or subcutaneous malignancies who were clinically assessed as eligible for bleomycin chemotherapy from a single centre in the UK. Patients were given TPCS2a on day 0 by slow intravenous injection, followed by a fixed dose of 15 000 IU/m(2) bleomycin by intravenous infusion on day 4. After 3 h, the surface of the target tumour was illuminated with 652 nm laser light (fixed at 60 J/cm(2)). The TPCS2a starting dose was 0·25 mg/kg and was then escalated in successive dose cohorts of three patients (0·5, 1·0, and 1·5 mg/kg). The primary endpoints were safety and tolerability of TPCS2a; other co-primary endpoints were dose-limiting toxicity and maximum tolerated dose. The primary analysis was per protocol. This study is registered with ClinicalTrials.gov, number NCT00993512, and has been completed.

FINDINGS

Between Oct 3, 2009, and Jan 14, 2014, we recruited 22 patients into the trial. 12 patients completed the 3-month follow-up period. Adverse events related to photochemical internalisation were either local, resulting from the local inflammatory process, or systemic, mostly as a result of the skin-photosensitising effect of TPCS2a. The most common grade 3 or worse adverse events were unexpected higher transient pain response (grade 3) localised to the treatment site recorded in nine patients, and respiratory failure (grade 4) noted in two patients. One dose-limiting toxicity was reported in the 1·0 mg/kg cohort (skin photosensitivity [grade 2]). Dose-limiting toxicities were reported in two of three patients at a TPCS2a dose of 1·5 mg/kg (skin photosensitivity [grade 3] and wound infection [grade 3]); thus, the maximum tolerated dose of TPCS2a was 1·0 mg/kg. Administration of TPCS2a was found to be safe and tolerable by all patients. No deaths related to photochemical internalisation treatment occurred.

INTERPRETATION

TPCS2a-mediated photochemical internalisation of bleomycin is safe and tolerable. We identified TPCS2a 0·25 mg/kg as the recommended treatment dose for future trials.

FUNDING

PCI Biotech.

Photochemical internalization of bleomycin and temozolomide--in vitro studies on the glioma cell line F98

Here we evaluate the photosensitizer meso-tetraphenyl chlorin disulphonate (TPCS2a) in survival studies of rat glioma cancer cells in combination with the novel photochemical internalization (PCI) technique. The tested anticancer drugs were bleomycin (BLM) and temozolomide (TMZ). Glioma cells were incubated with TPCS2a (0.2 μg ml(-1), 18 h, 37 °C) before BLM or TMZ stimulation (4 h) prior to red light illumination (652 nm, 50 mW cm(-2)). The cell survival after BLM (0.5 μm)-PCI (40 s light) quantified using the MTT assay was reduced to about 25% after 24 h relative to controls, and to 31% after TMZ-PCI. The supplementing quantification by clonogenic assays, using BLM (0.1 μm), indicated a long-term cytotoxic effect: the surviving fraction of clonogenic cells was reduced to 5% after light exposure (80 s) with PCI, compared to 70% in the case of PDT. In parallel, structural and morphological changes within the cells upon light treatment were examined using fluorescence microscopy techniques. The present study demonstrates that PCI of BLM is an effective method for killing F98 glioma cells, but smaller effects were observed using TMZ following the "light after" strategy. The results are the basis for further in vivo studies on our rat glioma cancer model using PDT and PCI.

Light-controlled endosomal escape of the novel CD133-targeting immunotoxin AC133-saporin by photochemical internalization - A minimally invasive cancer stem cell-targeting strategy

The cancer stem cell (CSC) marker CD133 is an attractive target to improve antitumor therapy. We have used photochemical internalization (PCI) for the endosomal escape of the novel CD133-targeting immunotoxin AC133-saporin (PCIAC133-saporin). PCI employs an endocytic vesicle-localizing photosensitizer, which generates reactive oxygen species upon light-activation causing a rupture of the vesicle membranes and endosomal escape of entrapped drugs. Here we show that AC133-saporin co-localizes with the PCI-photosensitizer TPCS2a, which upon light exposure induces cytosolic release of AC133-saporin. PCI of picomolar levels of AC133-saporin in colorectal adenocarcinoma WiDr cells blocked cell proliferation and induced 100% inhibition of cell viability and colony forming ability at the highest light doses, whereas no cytotoxicity was obtained in the absence of light. Efficient PCI-based CD133-targeting was in addition demonstrated in the stem-cell-like, triple negative breast cancer cell line MDA-MB-231 and in the aggressive malignant melanoma cell line FEMX-1, whereas no enhanced targeting was obtained in the CD133-negative breast cancer cell line MCF-7. PCIAC133-saporin induced mainly necrosis and a minimal apoptotic response based on assessing cleavage of caspase-3 and PARP, and the TUNEL assay. PCIAC133-saporin resulted in S phase arrest and reduced LC3-II conversion compared to control treatments. Notably, co-treatment with Bafilomycin A1 and PCIAC133-saporin blocked LC3-II conversion, indicating a termination of the autophagic flux in WiDr cells. For the first time, we demonstrate laser-controlled targeting of CD133 in vivo. After only one systemic injection of AC133-saporin and TPCS2a, a strong anti-tumor response was observed after PCIAC133-saporin. The present PCI-based endosomal escape technology represents a minimally invasive strategy for spatio-temporal, light-controlled targeting of CD133+ cells in localized primary tumors or metastasis.

The novel EpCAM-targeting monoclonal antibody 3-17I linked to saporin is highly cytotoxic after photochemical internalization in breast, pancreas and colon cancer cell lines

The epithelial cell adhesion molecule (EpCAM) is expressed by a wide range of human carcinomas, making it an attractive diagnostic and therapeutic target in oncology. Its recent identification on cancer stem cells has raised further interest in its use for tumor targeting and therapy. Here, we present the characterization and therapeutic potential of 3-17I, a novel human EpCAM-targeting monoclonal antibody. Strong reaction of 3-17I was observed in all lung, colon, and breast human tumor biopsies evaluated. By flow cytometry and confocal fluorescence microscopy, we demonstrate that 3-17I specifically targets EpCAM-positive cell lines. We also show evidence for mAb-sequestration in endo-/lysosomes, suggesting internalization of 3-17I by receptor-mediated endocytosis. The ribosomal-inactivating toxin saporin was linked to 3-17I, creating the per se non-toxic immunotoxin 3-17I-saporin, a promising candidate for the drug delivery technology photochemical internalization (PCI). PCI is based on a light-controlled destruction of endolysosomal membranes and subsequent cytosolic release of the sequestered payload upon light exposure. EpCAM-positive human cancer cell lines MCF7 (breast), BxPC-3 (pancreas), WiDr (colon), and the EpCAM-negative COLO320DM (colon), were treated with 3-17I-saporin in combination with the clinically relevant photosensitizer TPCS2a (Amphinex), followed by exposure to light. No cytotoxicity was observed after treatment with 3-17I-saporin without light exposure. However, cell viability, proliferation and colony-forming capacity was strongly reduced in a light-dependent manner after PCI of 3-17I. Our results show that 3-17I is an excellent candidate for diagnosis of EpCAM-positive tumors and for development of clinically relevant antibody-drug conjugates, using PCI for the treatment of localized tumors.

Photochemical internalisation, a minimally invasive strategy for light-controlled endosomal escape of cancer stem cell-targeting therapeutics

Despite progress in radio-, chemo- and photodynamic-therapy (PDT) of cancer, treatment resistance still remains a major problem for patients with aggressive tumours.

Abstract 1606: Photochemical internalization (PCI): a novel technology for site-specific drug delivery

The utilization of macromolecules in therapy of cancer and other diseases is becoming increasingly important. Recent advances in molecular biology and biotechnology have made it possible to improve targeting and design of cytotoxic agents, DNA complexes and other macromolecules for clinical applications. To achieve the expected biological effect of these macromolecules in many cases internalisation to the cell cytosol is crucial. At an intracellular level, the most fundamental obstruction for cytosolic delivery of therapeutic macromolecule is the membrane-barrier of the endocytic vesicles. Photochemical internalisation (PCI) is a novel technology for release of endocytosed macromolecules into the cytosol. The technology is based on the use of photosensitizers located in endocytic vesicles that upon activation by light induces rupture of the endocytic vesicles and thereby release of the macromolecules into the cytosol. PCI has been shown to enhance the biological activity of a large variety of macromolecules and other molecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins (RIPs), gene-encoding plasmids, adenovirus, oligonucleotides and the chemotherapeutic agent bleomycin. For clinical utilization a novel photosensitizer has been developed and evaluated for PCI of bleomycin. Preclinical results with this combination will be presented. Furthermore, a phase I/II dose-escalating clinical trial has been finalized and results from this trial will also be presented.

Citation Format: Kristian Berg, Colin Hopper, Anette Weyergang, Pål K. Selbo, Anders Høgset. Photochemical internalization (PCI): a novel technology for site-specific drug delivery. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1606. doi:10.1158/1538-7445.AM2013-1606

Photochemical targeting of antigens to the cytosol for stimulation of MHC class-I-restricted T-cell responses

Tumour chemotherapy with drugs is typically associated with severe systemic and local side effects for which reason immunotherapy represents a safer alternative. However, vaccination often fails to generate the required cytotoxic CD8 T-cell responses due to insufficient access of antigens to the cytosol and the MHC class I pathway of antigen presentation. One important issue of tumour research is therefore to develop strategies that allow cytosolic targeting or endosomal escape of tumour antigens. The objective of the current study was to test whether endocytosed antigen could be delivered to MHC class I by means of photochemical internalisation (PCI). Briefly, the antigen and the photosensitiser Amphinex were loaded in vitro onto bone-marrow-derived murine dendritic cells (DCs). After light activation, which is supposed to cause disruption of OVA- and Amphinex-containing endosomes, the DCs were cultured with OVA-specific CD8 T cells or used for immunisation of mice. PCI facilitated CD8 T-cell responses as measured by IFN-γ secretion in vitro and CD8 T-cell proliferation in vivo. In conclusion, the current proof-of-concept study is the first to describe PCI-mediated immunisation and the results revealed the feasibility of this novel technology in autologous vaccination for stimulation of CD8 T-cell responses.

Solubilization of the photosensitizers TPCS(2a) and TPPS(2a) in aqueous media evaluated by time-resolved fluorescence analysis

The pH-dependent aggregation of the novel photosensitizer TPCS(2a) is investigated at low concentration (c = 10(-6) M) in aqueous media by means of time-correlated single-photon counting, and compared to that of the chemically related photosensitizer TPPS(2a). The efficacy of selected solubilizers, i.e., various nonionic Pluronic block copolymers and the nonionic surfactant Tween 80, in inhibiting aggregation of the two photosensitizers is evaluated, which is important for the further formulation of TPCS(2a).

Abstract 3381: Photochemical internalization (PCI) of immunotoxins targeting cancer stem cell markers

The cancer stem cell (CSC) theory indicates that only a subset of the cancer cells is capable of tumor-initiation, self renewal and differentiation. CSC is also thought to be treatment resistant and responsible for recurrence. Different antigens are being used to identify CSC markers and are potential targets for CSC-based therapy. Due to the expression of the same antigens on normal stem cells it is of paramount importance that CSC-targeting cytotoxins are specifically and efficiently delivered to malignant tissues. Photochemical internalization (PCI) is a method for specific delivery of membrane impermeable macromolecules from endocytic vesicles to the cytosol of targeted cells. In this study we show that PCI increase the cytotoxic effect of immunotoxins (IT) targeting stem cell markers on different cell lines. The IT consists of a CSC-targeting mAb biotinylated to the ribosome inactivating plant (RIP) toxin saporin. TPCS2a-PCI of one of the ITs showed to be very cytotoxic at sub picomolar levels. Cytotoxicity of the IT was blocked by using excess concentration of unconjugated Ab. In addition, no difference in cytotoxicity was obtained between mAb-toxin and toxin alone in marker negative cell lines, confirming specificity. In order to asses enrichment of CSC-activity in vitro we used flow cytometry to sort cells based on the degree of expression of CSC-markers and compared the ability of different cell fractions to establish colonies in both 2D and 3D cell cultures growing in serum-free stem cell media. Cells with high expression of CSC-markers had significantly higher capacity to initiate colonies than low expressing cells. CSC enrichment was confirmed by an in vivo limiting dilution assay. The present study demonstrates that PCI is an efficient method for selective killing of cancer cells expressing stem cell markers and will be further explored for the targeting of tumors that express these markers.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3381. doi:1538-7445.AM2012-3381

Evaluation of physicochemical properties and aggregation of the photosensitizers TPCS2a and TPPS2a in aqueous media

Physicochemical properties of the novel photosensitizer meso-tetraphenyl chlorin disulphonate (TPCS2a) and the chemically related meso-tetraphenyl porphyrin disulphonate (TPPS2a) were investigated in aqueous solutions as part of pharmaceutical preformulation. Inflection points were calculated to be 3.9 for both compounds based on spectral shifts of aqueous solutions in the pH range 2-12, which likely correlate with indistinguishable pKa values of the imino nitrogens of the molecular cores. Accordingly, the fluorescence emission spectra showed pH dependent spectral shifts. Porphyrin-like compounds are known for aggregation in aqueous environments, and a small percentage of Tween 80 (0.006 % v/v = 4 x cmc) seemed to stabilize the aqueous samples of the two photosensitizers through hindrance of aggregation. The distribution coeffient of TPCS2a determined spectrophotometrically in 1-octanol/water is 0.4 (- 0.4 SD) and 1.5 (- 0.5 SD) for the reference TPPS2a. This confirms amphiphilicity which indicates preferred distribution and further restrain of diffusion in membranes, which is relevant for the use of TPCS2a as a photosensitizer in the process of photochemical internalization in vivo.

Physicochemical characterization of the photosensitizers TPCS2a and TPPS2a 1. Spectroscopic evaluation of drug--solvent interactions

The spectroscopic properties of the patented photosensitizer meso-tetraphenyl chlorin disulphonate (TPCS2a), intended for use in photochemical internalization (PCI) technology, and the chemically related photosensitizer meso-tetraphenyl porphyrin disulphonate (TPPS2a) were characterized in 14 organic solvents of varying polarity and amphiprotic properties. Absorption spectra and fluorescence emission spectra were acquired, and Stokes' shifts and fluorescence quantum yields determined. These investigations yield information on the physicochemical interactions between the photosensitizers and their surroundings (i.e., the physiological environment in vivo or the vehicle in vitro), which is essential for the further development of drug formulations. TPPS2a and TPCS2a are rigid molecules, built up by conjugated ring systems which possess limited interactions with the surroundings in the ground state (So). Accordingly, only small spectral shifts were observed in the absorption spectra, as well as in the fluorescence emission spectra. TPPS2a is spatially more planar than TPCS2a, which is twisted as a result of reduction of a double bond in the core. However, the two compounds were quite similarly influenced by properties of the solvents, indicating that twisting has limited importance in the interactions of the two photosensitizers with their environment. Both compounds possess a high character of pi-pi* transition upon light exposure, supported by high molar absorption coefficients. The fluorescence quantum yields (phi(f)) were influenced by solvent properties to a larger extent than the spectral shifts. This might indicate that the reactivity of the first excited singlet state (S1*) significantly depends on the properties of the surroundings.

Photochemical internalization (PCI): a technology for drug delivery

The utilization of macromolecules in therapy of cancer and other diseases is becoming increasingly relevant. Recent advances in molecular biology and biotechnology have made it possible to improve targeting and design of cytotoxic agents, DNA complexes, and other macromolecules for clinical applications. To achieve the expected biological effect of these macromolecules, in many cases, internalization to the cell cytosol is crucial. At an intracellular level, the most fundamental obstruction for cytosolic release of the therapeutic molecule is the membrane-barrier of the endocytic vesicles. Photochemical internalization (PCI) is a novel technology for release of endocytosed macromolecules into the cytosol. The technology is based on the use of photosensitizers located in endocytic vesicles that upon activation by light induces a release of macromolecules from their compartmentalization in endocytic vesicles. PCI has been shown to potentiate the biological activity of a large variety of macromolecules and other molecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins (RIPs), gene-encoding plasmids, adenovirus, oligonucleotides, and the chemotherapeutic bleomycin. PCI has also been shown to enhance the treatment effect of targeted therapeutic macromolecules. The present protocol describes PCI of an epidermal growth factor receptor (EGFR)-targeted protein toxin (Cetuximab-saporin) linked via streptavidin-biotin for screening of targeted toxins as well as PCI of nonviral polyplex-based gene therapy. Although describing in detail PCI of targeted protein toxins and DNA polyplexes, the methodology presented in these protocols are also applicable for PCI of other gene therapy vectors (e.g., viral vectors), peptide nucleic acids (PNA), small interfering RNA (siRNA), polymers, nanoparticles, and some chemotherapeutic agents.

Cytosolic Delivery of Liposomally Targeted Proteins Induced by Photochemical Internalization

PURPOSE

The application of therapeutic proteins is often hampered by limited cell entrance and lysosomal degradation, as intracellular targets are not reached. By encapsulation of proteins into targeted liposomes, cellular uptake via endocytosis can be enhanced. To prevent subsequent lysosomal degradation and promote endosomal escape, photochemical internalization (PCI) was studied here as a tool to enhance endosomal escape. PCI makes use of photosensitising agents which localize in endocytic vesicles, inducing endosomal release upon light exposure.

MATERIALS AND METHODS

The cytotoxic protein saporin was encapsulated in different types of targeted liposomes. Human ovarian carcinoma cells were incubated with the photosensitiser TPPS2a and liposomes. To achieve photochemical internalization, the cells were illuminated for various time periods. Cell viability was used as read-out. Illumination time and amount of encapsulated proteins were varied to investigate the influence of these parameters.

RESULTS

The cytotoxic effect of liposomally targeted saporin was enhanced by applying PCI, likely due to enhanced endosomal escape. The cytotoxic effect was dependent on the amount of encapsulated saporin and the illumination time.

CONCLUSION

PCI is a promising technique for promoting cytosolic delivery of liposomally targeted saporin. PCI may also be applicable to other liposomally targeted therapeutic proteins with intracellular targets.

Photochemical internalization enhances silencing of epidermal growth factor receptor through improved endosomal escape of siRNA

Photochemical internalization (PCI) has been employed as a tool for site-specific intracellular delivery of a variety of molecules. In this study, for the first time, PCI has been employed to facilitate the endosomal escape of small interfering RNA (siRNA) molecules, which are the functional mediators of RNA interference (RNAi). In order to interact with the machinery that will induce post-transcriptional gene silencing, siRNA molecules need to enter the cytoplasm of the cells. This study shows that one of the important rate-limiting steps of siRNA silencing efficiency is the ability of siRNA molecules and/or complexes to escape from the endosomes into the cytosol of the cells. The target of this study, the epidermal growth factor receptor (EGFR), is known as an attractive target for cancer therapy. In this study, a 10-fold increased efficiency in knockdown of the EGFR protein was obtained when anti-EGFR siRNA treatment was combined with PCI as compared to siRNA treatment alone. The fact that this combined treatment resulted in a stronger silencing efficiency indicates that lower doses of siRNA can be used when PCI is employed to augment siRNA delivery. Lowering doses of siRNA would prevent saturation of the RNAi machinery and reduce off-target effects. In addition, local illumination of target tissue would only induce PCI in the desired cells, which can further increase the specificity of the treatment, supporting PCI as an attractive strategy to improve siRNA silencing efficiency.