Presentation on theme: "Angela Dann Monday, October 9, 2006"— Presentation transcript:
1Angela Dann Monday, October 9, 2006 Photodynamic Therapy of Cancer: The Design and Characterization of Photosensitizing AgentsAngela DannMonday, October 9, 2006
2Photosensitizing Agents HistoryIntroductionProcess of Photodynamic therapy (PDT)PDT to treat cancerPhotosensitizing AgentsRequirementsAdvancementsTrials using PDT on tumor cellsConclusionsFuture applications
3History Light used as therapeutic agent for 3000+ years Egyptian, Indian, and Chinese civilizationsPsoriasis, rickets, vitiligo, skin cancerPhotodynamic Therapy (PDT) developed within the last centuryNature 2003, 3, 380.
5History Niels Finsen (late 19th century) Oscar Rabb (100+ years ago) Red light to prevent formation and discharge of small pox postulesUV light from the sun to treat cutaneous tuberculosisNobel Prize 1903Oscar Rabb (100+ years ago)Acridine in combination with certain wavelengths of lightLethal to infusoriaNature 2003, 3, 380.
6History Herman Von Tappeiner, A. Jesionek W. Hausmann Defined photodynamic actionTopically applied eosin and white lightW. Hausmann1st studies with haematoporphyrin and lightKilled paramecium and red blood cellsFriedrich Meyer-Betz (1913)1st to treat humans with porphyrinsHaematoporphyrin applied to skin, causing swelling/pain with light exposureNature 2003, 3, 380.
7History Samuel Schwartz (1960’s) Lipson, E.J. Baldes I. Diamond (1972) Developed haematoporphyrin derivative (HpD)Haematoporphyrin treated with acetic and sulfuric acids, neutralized with sodium acetateLipson, E.J. BaldesHpD localization in tumor cells, fluorescenceI. Diamond (1972)Use PDT to treat cancerNature 2003, 3, 380.
8History Thomas Dougherty (1975) J.F. Kelly (1976) Canada (1999) HpD and red lightEradicated mammary tumor growth in miceJ.F. Kelly (1976)1st human trials using HpDBladder cancerCanada (1999)1st PDT drug approvedNature 2003, 3, 380.
9Introduction: Process of Photodynamic therapy Two individually non-toxic components brought together to cause harmful effects on cells and tissuesPhotosensitizingagentLight of specificwavelengthNature 2003, 3, 380.
10Introduction: Reaction Mechanisms Type 1:Direct reaction with substrate (cell membrane or molecule)Transfer of H atom to form radicalsRadicals react with O2 to form oxygenated productsType 2:Transfer of energy to O2 to form 1O2Nature 2003, 3, 380.
11Introduction: Reaction Mechanisms Ratio of Type 1/Type 2 depends on:Photosensitizing agent, concentration of substrate and O2, binding affinity of photosensitizing agent to substrateReactive oxygenated species (ROS)Free radicals or 1O2Half-life of 1O2 < 0.04 msRadius affected < 0.02 mmNature 2003, 3, 380.
12Introduction: Type 1 and 2 Reactions Nature 2003, 3, 380.
13Introduction: Treatment of cancer PDT best suited for:Early stage tumorsInoperable for various reasonsLimited success due to lack of specificity and potency of photosensitizing agentsThree mechanisms of tumor damageNature 2003, 3, 380.
14Introduction: Mechanism 1 Direct Photodamage to Tumors by ROSProblems:Non-homogenous distribution of photosensitizing agent within tumorAvailability of O2 within tumor cellsReduction of O2 presence during PDTOvercoming O2 depletion:Lower light fluence ratePulse light delivery – allow re-oxygenationNature 2003, 3, J. of Nuclear Medicine 2006, 47, 1119.
15Introduction: Mechanism 2 Vascular DamageBlood vessels supply nutrients to tumor cellsEffects:Microvascular collapseTissue hypoxia and anoxiaThrombus formationAssociated with halting tumor growthAngiogenic factors upregulatedNature 2003, 3, J. of Nuclear Medicine 2006, 47, 1119.
16Introduction: Mechanism 3 Immune ResponseMovement of lymphocytes, leukocytes, macrophages into treated tissueDifference in reactions toward normal and tumor tissuesUpregulation of interleukin, not tumor necrosis factor-aNeutrophil – slows tumor growthRequired to purge remaining cellsNature 2003, 3, 380.
17Photosensitizing Agents: Requirements Selectivity to tumor cellsPhotostabilityBiological stabilityPhotochemical efficiencyNo cytotoxicity in absence of lightStrong absorption – nmGood tissue penetrationLong triplet excited state lifetimeJ. of Photochemistry and Photobiology A: Chemistry 2002, 153, Photochemistry and Photobiology 2001, 74, 656.
18Photosensitizing Agents: Classes Porphyrin derivativesMost widely usedChlorinsReduced porphyrinsDerivatives from chlorophyll or porphyrinsPhthalocyanines2nd generationContain diamagnetic metal ionPorphycenesSynthetic porphyrinsPharmaceutical Research 2000, 17, 1447.
20Photosensitizing Agents: Photofrin 1st clinical approval (1999) in CanadaBladder cancer treatmentMost commonly used photosensitizerDestroys mitochondriaDihematoporphyrin ether (DHE)bis-1-[3(1-hydroxy-ethyl)deuteroporphyrin-8-yl] ethyl etherActive component of HpDPhotochemistry and Photobiology 2001, 74, 656.
21Photosensitizing Agents: Photofrin Partially purified haematoporphyrin derivative (HpD)Mixture of mono-, di-, and oligomersTwice as phototoxic as crude haematoporphyrin (Hp)Crude Hp consists of range of porphyrinsConvert to HpD by acetylation and reduction using acetic and sulfuric acids, filtering, and neutralizing with sodium acetatePhotochemistry and Photobiology 2001, 74, 656. Nature 2003, 3, 380.
22Photosensitizing Agents: Photofrin Limitations:Contains 60 compoundsDifficult to reproduce compositionAt 630 nm, molar absorption coefficient is low (1,170 M-1 cm-1)Main absorption at 400 nmHigh concentrations of drug and light neededNot very selective toward tumor cellsAbsorption by skin cells causes long-lasting photosensitivity (½ life = 452 hr)Nature 2003, 3, J. of Photochemistry and Photobiology A: Chemistry 2002, 153, 245.
23Photosensitizing Agents: Advancements Need to overcome limitations of PhotofrinNew photosensitizers developed according to ideal situationsIncrease specificity to tumor cellsIncrease potencyDecrease time of sensitivity to sunlight after treatment
24Photosensitizing Agents: Foscan Chlorin photosensitizing agentApproved for treatment of head and neck cancerLow drug dose (0.1 mg/kg body weight)Low light dose (10 J/cm2)Complications due to potencyNature 2003, 3, 380.
25Photosensitizing Agents: 5-Aminolevulinic acid (5-ALA) Hydrophilic zwitterion at physiological pHApproved for treatment of actinic keratosis and BCC of skinTopical application most frequently usedEndogenous photosensitizing agent5-ALA not directly photosensitizingCreates porphyria-like syndromePrecursor to protoporphyrin IX (PpIX)Nature 2003, 3, 380. Photochemistry and Photobiology 2001, 74, 656. Pharmaceutical Res. 2000, 17, 1447.
26Photosensitizing Agents: Mono-L-aspartyl chlorin e6 (NPe6) 2nd generation hydrophilic chlorinDerived from chlorophyll aChemically pureAbsorption at 664 nmLocalizes in lysosomes (instead of mitochondria)Reduced limitations compared to PhotofrinDecreased sensitivity to sunlight (1 week)½ life = hrPhotodermatol Photoimmunol Photomed 2005, 21, 72.
27Photosensitizing Agents: Phthalocyanines 2nd generationRing of 4 isoindole units linked by N-atomsStable chelates with metal cationsSulfonate groups increase water solubilityExamples (AlPcS4, ZnPcS2)Aluminum chlorophthalocyanine sulfonateMore prolonged photosensitization than HpDLess skin sensitivity in sunlightPhotochemistry and Photobiology 2001, 74, 656. J. of Nuclear Medicine, 2006, 47, 1119.
28Photosensitizing Agents: Phthalocyanines Tetrasulfonated AlPcS4HydrophilicDeposited in vascular stromaAffects vascular system – indirect cell deathDisulfonated ZnPcS2AmphophilicTransported by lipoproteinsDirect cell deathPhotochemistry and Photobiology 2001, 74, 656. J. of Nuclear Medicine, 2006, 47, 1119.
29Photosensitizing Agents: Meta-tetra(hydroxyphenyl)porphyrins (mTHPP) Commercially available as meta-tetra(hydroxyphenyl)chlorin – (mTHPC)2nd generationImproved red light absorption25-30 times more potent than HpDMore selective toward tumor cellsMost active photosensitizer with low drug and light dosesNot granted approvalPhotochemistry and Photobiology 2001, 74, 656. Int. J. Cancer 2001, 93, 720.
30Photosensitizing Agents: Texaphyrins Synthetic – porphyceneWater solubleRelated to porphyrinsAbsorption between nm (far red)Sufficiently penetrates tissuePhotochemistry and Photobiology 2001, 74, 656.
31Photosensitizing Agents: Tin ethyl etiopurpurin SnET2, PurlytinChlorinTreatment of cutaneous metastatic malignanciesResults of phase III study (934 patients) not yet releasedPhotochemistry and Photobiology 2001, 74, 656.
32PDT Trials on Tumor Cells: Breast Cancer Chest wall recurrences – problem with mastectomy treatment (5-19%)Study:7 patients, 57.6 years old (12.6)89 metastatic nodes treated11 PDT sessionsPhotosensitizing agent: (m-THPC)meta-tetra(hydroxyphenyl)chlorin2nd generation photosensitizing agentInt. J. Cancer 2001, 93, 720.
33PDT Trials on Tumor Cells: Breast Cancer Dosage:Diode laser used to generate l = 652 nm3 patients0.10 mg/kg total body weight48 hr under 5 J/cm24 patients0.15 mg/kg total body weight96 hr under 10 J/cm2Int. J. Cancer 2001, 93, 720.
34PDT Trials on Tumor Cells: Breast Cancer Results:Complete response in all 7 patientsPain – 10 days, Healing – 8-10 weeksPatients advised to use sun block or clothing to protect skin from light for 2 weeks4 days after treatment – 1 patient with skin erythema and edema from reading light6 of 7 patients given medication for painMostly based on size, not lightdoseRecurrences in 2 patients (2 months)Int. J. Cancer 2001, 93, 720.
35PDT Trials on Tumor Cells: Skin Cancer Traditional Treatments:Surgery, electrodesiccation, cryosurgery, topical application of podophyllin or 5-fluorouracil, radiationProblems:High cost, scarring, pigmentation changes, pain, inflammation, irritationPharmaceutical Research 2000, 17, 1447.
36PDT Trials on Tumor Cells: Skin Cancer Most promising treatment using PDTSkin highly accessible to light exposureMost common methodTopical administration of 5-ALANon-invasive, short photosensitization period, treat multiple lesions, good cosmetic results, well accepted by patients, no side effectsPharmaceutical Research 2000, 17, 1447.
37PDT Trials on Tumor Cells: Skin Cancer Mechanism of 5-ALA use:5-ALA formed in vivo in mitochondria by condensation of glycine and succinyl CoA (catalyzed by ALA-syntase)Subsequent reactions produce protoporphyrin IX (PpIX)Converted to heme using ferrochelatase and FeHeme inhibits synthesis of 5-ALAExcess administered 5-ALA passes through abnormal epidermis and converts to PpIXPharmaceutical Research 2000, 17, 1447.
38PDT Trials on Tumor Cells: Skin Cancer Mechanism (continued):PpIX accumulates with minimized amount of ferrochelataseTissues with increased concentration of PpIX undergo phototoxic damage upon light exposure3PpIX is formed, energy transferred to create 1O2PpIX nearly completely cleared within 24 hrPharmaceutical Research 2000, 17, 1447.
39PDT Trials on Tumor Cells: Skin Cancer Clinical Studies performed on superficial skin cancer types:Actinic keratosis (AK)Basal cell carcinoma (BCC)Squamous cell carcinoma (SCC)Bowen’s disease (BD)Complete response (CR) – no clinical or histopathologic signs after follow-upMinimal side effectsPharmaceutical Research 2000, 17, 1447.
40PDT Trials on Tumor Cells: Skin Cancer Pharmaceutical Research 2000, 17, 1447.
41PDT Trials on Tumor Cells: Skin Cancer Clinical trials with mono-L-aspartyl chlorin e6 (NPe6)14 patients – 9 male, 5 female46-82 years old (64 yrs average)BCC – 22 lesions, SCC – 13 lesions, papillary carcinoma – 14 lesionsPhotodermatol Photoimmunol Photomed 2005, 21, 72.
42PDT Trials on Tumor Cells: Skin Cancer Clinical trials (continued)5 different intravenous doses of NPe6 over 30 minutes (0.5 mg/kg – 3.5 mg/kg)4-8 hr prior to light administration (due to number of lesions)Light dose – J/cm2Argon-pumped tunable dye laser set at 664 nmDose dependent on tumor size/shapePhotodermatol Photoimmunol Photomed 2005, 21, 72.
43PDT Trials on Tumor Cells: Skin Cancer Photodermatol Photoimmunol Photomed 2005, 21, 72.
44PDT Trials on Tumor Cells: Skin Cancer Results:4 weeks later: 20 of 22 BCC – CR, 18 of 27 other – CRCR – no evidence of tumor in treatment fieldPR – >50% reduction in tumor sizePhotosensitivity gone within 1 week (12 of 14)3 patients – mild to moderate pruritis, facial edema or blistering, erythema, tingling1 patient – severe intermittent burning pain1 patient – erythema, edema, moderate pain (gone within 2 weeks)Photodermatol Photoimmunol Photomed 2005, 21, 72.
45Conclusions PDT of cancer regulated by: Type of photosensitizing agent Type of administrationDose of photosensitizerLight doseFluence rateO2 availabilityTime between administration of photosensitizer and light
46ConclusionsTumor cells show some selectivity for photosensitizing agent uptakeLimited damage to surrounding tissuesLess invasive approachOutpatient procedureVarious application typesWell accepted cosmetic results
47Conclusions: Clinical Approval of Photosensitizers Nature 2003, 3, 380.
48Future Applications: Treatment of Other Diseases DermatologyPsoriasis, scleroderma, vitiligoRheumatologyArthritisCardiovascular diseasesArtherosclerotic plaque resolution, post-stent implantationAge-related eye diseasesMacular degenerationImmunotherapyNature 2003, 3, 380. Photochemistry and Photobiology 2001, 74, 656.
49Future Applications: Tumor Detection Using Fluorescence Mechanism by which HpD selectively accumulates in tumor cells – not well understoodHigh vascular permeability of agents?Testing photosensitizing agents:Porphyrins, haematoporphyrins, HpD, ALA-DAdminister photosensitizer and monitor fluorescence with endoscopeSCC shows increased fluorescenceMore invasive tumors show even greater fluorescenceNature 2003, 3, 380.
50Future Applications: Tumor Detection Using Fluorescence a: Green vascular endothelial cells of a tumorb: Red photosensitizing agent localizes to vascular endothelial cells after intravenous injectionNature 2003, 3, 380.
51Future Applications: Photosensitizing Drugs Improved Specificity and PotencyBetter photosensitizers developed and under investigation in clinical trialsUse of carriers – conjugated antibodies directed to tumor-associated antigensNew compounds that absorb light of longer wavelength – better tissue penetrationNew compounds with less skin photosensitivityImproved EfficacyCreating a preferred treatment of cancerNature 2003, 3, 380.