Yongen Sun

Biodistribution and antitumour efficacy of long-circulating N-(2-hydroxypropyl)methacrylamide copolymer–doxorubicin conjugates in nude mice

The aim of this study was to evaluate the influence of the molecular weight (mol. wt) of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-doxorubicin (DOX) conjugates (P-DOX) on biodistribution and therapeutic efficacy in nu/nu mice bearing human ovarian carcinoma OVCAR-3 xenografts. Copolymerisation of HPMA, a polymerisable derivative of DOX (N-methacryloylglycylphenylalanylleucylglycyl doxorubicin) and a newly designed crosslinking agent, N(2),N(5)-bis(N-methacryloylglycylphenylalanyl-leucylglycyl)ornithine methyl ester monomers resulted in novel, high mol. wt, branched, water-soluble P-DOX containing lysosomally degradable oligopeptide sequences as crosslinks and side-chains terminated in DOX. Four conjugates with mol. wt of 22, 160, 895 and 1230 kDa were prepared. The results indicated that the half-life in blood and the elimination rate from the tumour were up to 28 times longer and 25 times slower, respectively, for P-DOX (mol. wt=1230 kDa) than for free DOX. Treatment with P-DOX (mol. wt > or = 160 kDa) inhibited tumour growth more efficiently than that of 22 kDa P-DOX or free DOX (P<0.02) at a 2.2 mg/kg DOX equivalent dose. In conclusion, the administration of long circulating P-DOX resulted in enhanced tumour accumulation with a concomitant increase in therapeutic efficacy.

A polymeric drug delivery system for the simultaneous delivery of drugs activatable by enzymes and/or light

Three water soluble copolymers based on N-(2-hydroxypropyl)methacrylamide were prepared. Copolymer I contains adriamycin, a chemotherapeutic agent, attached via enzymatically degradable oligopeptide (glycylphenylalanylleucylglycine; G-F-L-G) side chains. The other two copolymers contained the photosensitizer, meso-chlorin e6 monoethylene diamine disodium salt (Mce6). In Copolymer II, the chlorin is attached via the degradable G-F-L-G sequence, and it was bound by the nondegradable glycyl spacer in Copolymer III. Initially, the copolymers were characterized separately in vitro and in vivo. Combinations of the copolymer bound chemotherapeutic agent and each of the copolymer bound photosensitizers were then assessed for antitumor effect in vivo. Localization/retention studies (A/J mice; Neuro 2A neuroblastoma solid tumor) were performed with the two copolymers containing Mce6 as well as the free drug. Results of these experiments demonstrated a very different tumor uptake profile for the two copolymers. While the free drug was rapidly cleared from tumor tissue, the copolymer containing Mce6 attached via the non-degradable bond was retained for an extended period; drug concentrations in the tumor were high even after 5 days. On the other hand, a high concentration of the copolymer containing Mce6 bound via the degradable sequence was taken up by the tumor, yet its concentration in the tumor was substantially diminished at 48 h after administration. This shows indirect evidence of in vivo cleavage of Mce6 from the copolymer in the lysosomal compartment which is supported by direct evidence of cleavage by cathepsin B (a lysosomal enzyme) in vitro. Antitumor effects were assessed on Neuro 2A neuroblastoma induced in A/J mice for all three copolymers. Photodynamic therapy (PDT) proved the copolymer with Mce6 bound via the degradable oligopeptide sequence to be a more effective photosensitizer in vivo than the other chlorin containing copolymer. The difference in activity was consistent with the results obtained by photophysical analyses in which the free drug had a higher quantum yield of singlet oxygen generation than the polymer bound drug in buffer. The quantum yield of singlet oxygen generation increased with the enzymatic cleavage of the chlorin from the copolymer. Conditions were subsequently determined for which chemotherapy or PDT would show some antitumor effect, yet be incapable of curing tumors. Finally, combination therapy experiments were performed in which the copolymer bound adriamycin was mixed with either of the copolymer bound chlorin compounds and injected intravenously (i.v.) into the tail veins of mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Combination chemotherapy and photodynamic therapy of targetable N-(2-hydroxypropyl)methacrylamide copolymer–doxorubicin/mesochlorin e6-OV-TL 16 antibody immunoconjugates

The aim of this study was to evaluate the combination chemotherapy and photodynamic therapy of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-bound doxorubicin (DOX) and mesochlorin e(6) (Mce(6)) targeted with an OV-TL 16 monoclonal antibody (P-DOX-Ab and P-Mce(6)-Ab, respectively) in nude mice bearing human ovarian OVCAR-3 carcinoma xenografts. P-DOX-Ab and P-Mce(6)-Ab were synthesized by first conjugating DOX or Mce(6) to an HPMA copolymer precursor (Mw=21000), then reacting with OV-TL 16 antibody. The immunoconjugates were purified by size exclusion chromatography on Superose 6 column and analyzed. The Mce(6) concentration in tissues was determined by a fluorescence assay. Eighteen hours after administration, the tumors received a light dose of 220 J/cm(2) from a KTP 650-nm dye-laser. P-DOX-Ab and P-Mce(6)-Ab had polymer:drug:protein weight ratios of 32:3:62 and 26:2:72, corresponding to polymer:drug:protein molecular ratios of approximately 4:14:1 and 3:8:1, respectively. The biodistribution results indicated that the percentage of total administered dose of Mce(6) in tumors reached approximately 1% for the nontargeted conjugate at 18 h after administration, while that of P-Mce(6)-Ab was approximately 13 times higher. Nude mice bearing OVCAR-3 xenografts that received one i.v. dose of P-DOX-Ab (2.2 mg/kg DOX equivalent) and P-Mce(6)-Ab (1.5 mg/kg Mce(6) equivalent) with light irradiation achieved a xenograft cure rate of more than 60%. The incorporation of OV-TL 16 antibody dramatically enhanced the accumulation in tumors with a concomitant increase in the therapeutic efficacy of P-DOX-Ab and P-Mce(6)-Ab in combination therapy, which may probably be attributed to both antibody targeting and enhanced permeability and retention (EPR) effects.

Synthesis and evaluation of a backbone biodegradable multiblock HPMA copolymer nanocarrier for the systemic delivery of paclitaxel

The performance and safety of current antineoplastic agents, particularly water-insoluble drugs, are still far from satisfactory. For example, the currently widely used Cremophor EL®-based paclitaxel (PTX) formulation exhibits pharmacokinetic concerns and severe side effects. Thus, the concept of a biodegradable polymeric drug-delivery system, which can significantly improve therapeutic efficacy and reduce side effects is advocated. The present work aims to develop a new-generation of long-circulating, biodegradable carriers for effective delivery of PTX. First, a multiblock backbone biodegradable N-(2-hydroxypropyl)methacrylamide(HPMA) copolymer-PTX conjugate (mP-PTX) with molecular weight (Mw) of 335 kDa was synthesized by RAFT (reversible addition-fragmentation chain transfer) copolymerization, followed by chain extension. In vitro studies on human ovarian carcinoma A2780 cells were carried out to investigate the cytotoxicity of free PTX, HPMA copolymer-PTX conjugate with Mw of 48 kDa (P-PTX), and mP-PTX. The experiments demonstrated that mP-PTX has a similar cytotoxic effect against A2780 cells as free PTX and P-PTX. To further compare the behavior of this new biodegradable conjugate (mP-PTX) with free PTX and P-PTX in vivo evaluation was performed using female nu/nu mice bearing orthotopic A2780 ovarian tumors. Pharmacokinetics study showed that high Mw mP-PTX was cleared more slowly from the blood than commercial PTX formulation and low Mw P-PTX. SPECT/CT imaging and biodistribution studies demonstrated biodegradability as well as elimination of mP-PTX from the body. The tumors in the mP-PTX treated group grew more slowly than those treated with saline, free PTX, and P-PTX (single dose at 20 mg PTX/kg equivalent). Moreover, mice treated with mP-PTX had no obvious ascites and body-weight loss. Histological analysis indicated that mP-PTX had no toxicity in liver and spleen, but induced massive cell death in the tumor. In summary, this biodegradable drug delivery system has a great potential to improve performance and safety of current antineoplastic agents.

Biodistribution of free and N-(2-hydroxypropyl)methacrylamide copolymer-bound mesochlorin e6 and adriamycin in nude mice bearing human ovarian carcinoma OVCAR-3 xenografts

The purpose of this study was to examine the biodistribution of the photosensitizing drug, mesochlorin e(6) monoethylenediamine (Mce(6)), and the antineoplastic agent, adriamycin (ADR), as well as their N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugates in female nu/nu athymic mice bearing human ovarian carcinoma OVCAR-3 xenografts. The levels of Mce(6) and HPMA copolymer-bound Mce(6) in tissues were assayed spectrophotometrically, while the levels of ADR and HPMA copolymer-bound ADR were determined using high-performance liquid chromatography. It appeared that the circulation lifetimes of HPMA copolymer-bound Mce(6) and ADR were three times more than those of the drugs in the free form. The concentrations of the HPMA copolymer-conjugated drugs in tumor reached maximum levels 18 h post injection. Intravenous injection routinely gave higher tissue levels of the drugs than intraperitoneal administration at time intervals less than 24 h. The biodistribution of the HPMA copolymer-bound drugs in tumor-bearing mice was significantly different from that of the free drugs, which is important in optimizing the treatment protocols. In particular, the HPMA copolymer-conjugated drugs accumulated at significantly higher levels in tumor tissues. This effect is attributed to the increased vascular permeability and reduced lymphatic drainage characteristic of tumor tissues [enhanced permeability and retention (EPR) effect].

Contrast-Enhanced MRI-Guided Photodynamic Cancer Therapy with a Pegylated Bifunctional Polymer Conjugate

PurposeTo study contrast-enhanced MRI guided photodynamic therapy with a pegylated bifunctional polymer conjugate containing an MRI contrast agent and a photosensitizer for minimally invasive image-guided cancer treatment.MethodsPegylated and non-pegylated poly-(l-glutamic acid) conjugates containing mesochlorin e6, a photosensitizer, and Gd(III)-DO3A, an MRI contrast agent, were synthesized. The effect of pegylation on the biodistribution and tumor targeting was non-invasively visualized in mice bearing MDA-MB-231 tumor xenografts with MRI. MRI-guided photodynamic therapy was carried out in the tumor bearing mice. Tumor response to photodynamic therapy was evaluated by dynamic contrast enhanced MRI and histological analysis.ResultsThe pegylated conjugate had longer blood circulation, lower liver uptake and higher tumor accumulation than the non-pegylated conjugate as shown by MRI. Site-directed laser irradiation of tumors resulted in higher therapeutic efficacy for the pegylated conjugate than the non-pegylated conjugate. Moreover, animals treated with photodynamic therapy showed reduced vascular permeability on DCE-MRI and decreased microvessel density in histological analysis.ConclusionsPegylation of the polymer bifunctional conjugates reduced non-specific liver uptake and increased tumor uptake, resulting in significant tumor contrast enhancement and high therapeutic efficacy. The pegylated poly(l-glutamic acid) bifunctional conjugate is promising for contrast enhanced MRI guided photodynamic therapy in cancer treatment.

Contrast enhanced MRI‐guided photodynamic therapy for site‐specific cancer treatment

Photodynamic therapy (PDT) is a minimally invasive and effective approach for cancer treatment. It is potentially useful for treating tumors that are not accessible to surgery, radiation, or destructive ablations, and are resistant to chemotherapy. Efficacious treatment of interstitial tumors with PDT requires efficient delivery of photosensitizers and accurate location of tumor tissues for effective light irradiations. In this study we performed contrast‐enhanced (CE) MRI‐guided PDT with a bifunctional polymer conjugate containing both a magnetic resonance imaging (MRI) contrast agent and a photosensitizer, poly(L‐glutamic acid) (PGA)‐(Gd‐DO3A)‐mesochlorin e6 (Mce6). The efficacy of the bifunctional conjugate in cancer CE‐MRI and cancer treatment was evaluated in athymic nude mice bearing MDA‐MB‐231 human breast carcinoma xenografts, with PGA‐(Gd‐DO3A) used as a control. The polymer conjugates preferentially accumulated in the solid tumor due to the hyperpermeability of the tumor vasculature, resulting in significant tumor enhancement for accurate tumor detection and localization by MRI. Significant therapeutic response was observed for PDT with the bifunctional conjugate as compared to the control. CE‐MRI‐guided PDT with the bifunctional conjugate is effective for tumor detection and minimally invasive cancer treatment. Magn Reson Med, 2006.

Antitumor Efficacy of Colon-Specific HPMA Copolymer/9-Aminocamptothecin Conjugates in Mice Bearing Human-Colon Carcinoma Xenografts

The antitumor activity of a colon-specific N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer - 9-aminocamptothecin (9-AC) conjugate (P-9-AC) was assessed in orthotopic and subcutaneous animal (HT29 xenograft) tumor models. P-9-AC treatment of mice bearing orthotopic colon tumors, with a dose of 3 mg/kg of 9-AC equivalent every other day for 6 weeks, resulted in regression of tumors in 9 of 10 mice. A lower dose of P-9-AC (1.25 mg/kg of 9-AC equivalent) every other day for 8 weeks inhibited subcutaneous tumor growth in all mice. No liver metastases were observed. Colon-specific release of 9-AC from polymer conjugates enhanced antitumor activity and minimized the systemic toxicity.

Mucoadhesive hybrid gel improves intraperitoneal platinum delivery.

A leading cause of death and suffering in patients with abdominal or pelvic malignancies is progression of peritoneal surface disease. Changes in the use of chemotherapy have shown significant survival benefits for intraperitoneal or combined intraperitoneal and intravenous treatment following optimal surgical cytoreduction. However, broader clinical use of intraperitoneal therapy has not reached its full potential due to limited efficacy, accessibility and nonspecific toxicity. To overcome these problems, we developed a mucoadhesive hybrid gel (HG) for a local, intraperitoneal drug delivery. In vivo studies confirmed reliable adherence and residence of the gel to the peritoneal sidewall for at least 72 h exhibiting no signs of tissue toxicity. Functionally active CDDP was released from HG within 2h and was equal to free CDDP in vitro. Moreover, intraperitoneal application of HG-CDDP significantly enhanced CDDP accumulation in the genomic DNA of peritoneal tissues compared to the same CDDP dose administered intravenously. These findings indicate the potential application of this hybrid gel as a mucoadhesive drug carrier amendable to use for intraperitoneal drug delivery and possible expansion for use on other mucosal surfaces of the female reproductive tract.

Intraoperative Phototherapy: A Comparative Study of Intravenous and Topical Photofrin II and Aminolevulinic Acid

This study compares the systemic and topical application of photofrin II and aminolevulinic acid as an intraoperative adjuvant therapy in the C3H mouse radiation-induced fibrosarcoma model. Dose-development and time-dependent studies were first conducted followed by intraoperative phototherapy studies with photofrin II and aminolevulinic acid. Study results clearly show that intraoperative phototherapy after aminolevulinic acid topical application is significantly more effective than treatment with photofrin II given intravenously or topically (p < 0.05) in this animal tumor model. The concept of topical application of photosensitizers and the rationale for intraoperative adjuvant phototherapy are discussed.