Design and Preclinical Evaluation of a Novel B7-H4-Directed Antibody-Drug Conjugate, AZD8205, Alone and in Combination with the PARP1-Selective Inhibitor AZD5305

PURPOSE

We evaluated the activity of AZD8205, a B7-H4-directed antibody-drug conjugate (ADC) bearing a novel topoisomerase I inhibitor (TOP1i) payload, alone and in combination with the PARP1-selective inhibitor AZD5305, in preclinical models.

EXPERIMENTAL DESIGN

IHC and deep-learning-based image analysis algorithms were used to assess prevalence and intratumoral heterogeneity of B7-H4 expression in human tumors. Several TOP1i-ADCs, prepared with Val-Ala or Gly-Gly-Phe-Gly peptide linkers, with or without a PEG8 spacer, were compared in biophysical, in vivo efficacy, and rat toxicology studies. AZD8205 mechanism of action and efficacy studies were conducted in human cancer cell line and patient-derived xenograft (PDX) models.

RESULTS

Evaluation of IHC-staining density on a per-cell basis revealed a range of heterogeneous B7-H4 expression across patient tumors. This informed selection of bystander-capable Val-Ala-PEG8-TOP1i payload AZ14170133 and development of AZD8205, which demonstrated improved stability, efficacy, and safety compared with other linker-payload ADCs. In a study of 26 PDX tumors, single administration of 3.5 mg/kg AZD8205 provided a 69% overall response rate, according to modified RECIST criteria, which correlated with homologous recombination repair (HRR) deficiency (HRD) and elevated levels of B7-H4 in HRR-proficient models. Addition of AZD5305 sensitized very low B7-H4-expressing tumors to AZD8205 treatment, independent of HRD status and in models representing clinically relevant mechanisms of PARPi resistance.

CONCLUSIONS

These data provide evidence for the potential utility of AZD8205 for treatment of B7-H4-expressing tumors and support the rationale for an ongoing phase 1 clinical study (NCT05123482). See related commentary by Pommier and Thomas, p. 991.

A Hoechst Reporter Enables Visualization of Drug Engagement In Vitro and In Vivo: Toward Safe and Effective Nanodrug Delivery

Assessment of drug activation and subsequent interaction with targets in living tissues could guide nanomedicine design, but technologies enabling insight into how a drug reaches and binds its target are limited. We show that a Hoechst-based reporter system can monitor drug release and engagement from a nanoparticle delivery system in vitro and in vivo, elucidating differences in target-bound drug distribution related to drug-linker and nanoparticle properties. Drug engagement is defined as chemical detachment of drug or reporter from a nanoparticle and subsequent binding to a subcellular target, which in the case of Hoechst results in a fluorescence signal. Hoechst-based nanoreporters for drug activation contain prodrug elements such as dipeptide linkers, conjugation handles, and nanoparticle modifications such as targeting ligands to determine how nanomedicine design affects distribution of drug engaged with a subcellular target, which is tracked via cellular nuclear fluorescence in situ. Furthermore, the nanoplatform is amenable toward common maleimide-based linkers found in many prodrug-based delivery systems including polymer-, peptide-, and antibody-drug conjugates. Findings from the Hoechst reporter system were applied to develop highly potent, targeted, anticancer micelle nanoparticles delivering a monomethyl auristatin E (MMAE) prodrug comprising the same linkers employed in Hoechst studies. MMAE nanomedicine with the optimal drug-linker resulted in effective tumor growth inhibition in mice without associated acute toxicity, whereas the nonoptimal linker that showed broader drug activation in Hoechst reporter studies resulted in severe toxicity. Our results demonstrate the potential to synergize direct visualization of drug engagement with nanomedicine drug-linker design to optimize safety and efficacy.

Cyclopentadiene as a Multifunctional Reagent for Normal- and Inverse-Electron Demand Diels-Alder Bioconjugation

Optimizing the Diels-Alder (DA) reaction for aqueous coupling has resulted in practical methods to link molecules such as drugs and diagnostic agents to proteins. Both normal electron demand (NED) and inverse electron demand (IED) DA coupling schemes have been employed, but neither mechanism entails a common multipurpose reactive group. This report focuses on expanding the bioconjugation toolbox for cyclopentadiene through the identification of reactive groups that couple through NED or IED mechanisms in aqueous solution. Dienophiles and tetrazine derivatives were screened for reactivity and selectivity toward antibodies bearing cyclopentadiene amino acids to yield bioconjugates. Twelve NED dienophiles and four tetrazine-based IED substrates were identified as capable of practical biocoupling. Furthermore, tetrazine ligation to cyclopentadiene occurred at a rate of 3.3 ± 0.5 M^-1 s^-1 and was capable of bioorthogonal transformations, as evidenced by the selective protein labeling in serum. Finally, an antibody-drug conjugate (ADC)-bearing monomethyl auristatin E was prepared via tetrazine conjugation to cyclopentadiene. The resulting ADC was stable and demonstrated potent activity in vitro. These findings expand the utility of cyclopentadiene as a tool to couple entities to proteins via dual DA addition mechanisms.

Abstract 1765: Discovery and first disclosure of AZD8205, a B7-H4-targeted antibody-drug conjugate utilizing a novel topoisomerase I linker-warhead

The cell-surface glycoprotein B7-H4 is overexpressed in a range of solid tumors including breast cancer, ovarian serous carcinoma, endometrial carcinoma, and cholangiocarcinoma, yet has limited expression in normal tissue, making it an attractive target for an antibody-drug conjugate (ADC). This presentation describes for the first time the development of AZD8205, a B7-H4 targeted ADC incorporating a novel topoisomerase 1 inhibitor (TOP1i) linker-warhead, AZ’0133 which was designed to exploit the full potential of B7-H4 as an ADC target. Initially, we investigated a series of more than 35 TOP1i compounds as warheads and achieved activity in a clinically relevant nM range. We further optimized the conjugation site and chemistry to reduce the potential for aggregation while maintaining potency, overcoming major synthetic challenges to deliver a robust synthetic route amenable to scale-up. Finally, with a series of optimized linker-warheads, we explored the impact of linker-warhead design on ADC hydrophobicity, stability, efficacy, pharmacokinetics and tolerability culminating in the development of AZD8205. The primary mechanism of action of AZD8205 is intracellular delivery of the TOP1i warhead to B7-H4 positive cells, leading to DNA damage and apoptotic cell death. AZD8205 drove bystander killing of target negative cells in mixed cultures in vitro, which is further supported by robust antitumor activity observed in in vivo studies with patient-derived xenograft (PDX) tumors with heterogeneous target expression, representing multiple tumor indications. In a study of 26 human TNBC PDX tumors, a single IV administration of 3.5 mg/kg AZD8205 provided an overall response rate of 69% (tumor regression of 30% or greater from baseline) and complete responses observed in 9/26 (36%) of models. To understand the biology underlying antitumor response, we conducted a multiparametric analysis including genomics, proteomics and computational pathology and found that deeper antitumor activity was observed in models with elevated B7-H4 expression as well as in models with defects in DNA damage repair (DDR). To further exploit the DNA damage elicited by the TOP1i warhead, we examined combinations of AZD8205 with small molecules, including a novel PARP1 selective inhibitor, in a BRCA wild type MDA-MB-468 model. These data suggest that AZD8205 is a promising therapeutic candidate for the treatment of B7-H4 positive solid tumors. A first in human phase 1 study in patients with advanced solid tumors is currently ongoing (NCT05123482).

Citation Format: Krista Kinneer, Niall J. Dickinson, Luke Masterson, Thais Cailleau, Ian Hutchinson, Balakumar Vijayakrishnan, Nazzareno Dimasi, R. James Christie, Mary McFarlane, Kathryn Ball, Arthur Lewis, Sofia Koch, Lee Brown, Yue Huang, Anton I. Rosenbaum, Jiaqi Yuan, Si Mou, Noel R. Monks, Jon Chesebrough, Ravinder Tammali, Judith Anderton, Darrin Sabol, Frances Anne Tosto, Philipp Wortmann, Zachary A. Cooper, Pauline Ryan, John Hood, Carlos Fernandez Teruel, Carlos Serra Traynor, Andy Pike, Michael Davies, Elisabetta Leo, Kimberly Cook, Nadia Luheshi, Philip W. Howard, Puja Sapra. Discovery and first disclosure of AZD8205, a B7-H4-targeted antibody-drug conjugate utilizing a novel topoisomerase I linker-warhead [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1765.

Metabolite-Based Modification of Poly(l-lysine) for Improved Gene Delivery

Synthetic gene delivery systems employ multiple functions to enable safe and effective transport of DNA to target cells. Here, we describe metabolite-based poly(l-lysine) (PLL) modifiers that improve transfection by imparting both pH buffering and nanoparticle stabilization functions within a single molecular unit. PLL modifiers were based on morpholine (M), morpholine and niacin (MN), or thiomorpholine (TM). PLL modification with (MN) or (TM) imparted buffering function over the pH range of 5-7 both in solution and live cells and enhanced the stability of PLL DNA nanoparticles, which exhibited higher resistance to polyanion exchange and prolonged blood circulation. These properties translated into increased transfection efficiency in vitro coupled with reduced toxicity compared to unmodified PLL and PLL(M). Furthermore, PEG-PLL(MN) DNA nanoparticles transfected muscle tissue in vivo for >45 days following intramuscular injection. These polymer modifiers demonstrate the successful design of multifunctional units that improve transfection of synthetic gene delivery systems while maintaining biocompatibility.

A Diene-Containing Noncanonical Amino Acid Enables Dual Functionality in Proteins: Rapid Diels-Alder Reaction with Maleimide or Proximity-Based Dimerization

Here, we describe a diene-containing noncanonical amino acid (ncAA) capable of undergoing fast and selective normal electron-demand Diels-Alder (DA) reactions following its incorporation into antibodies. A cyclopentadiene derivative of lysine (CpHK) served as the reactive handle for DA transformations and the substrate for genetic incorporation. CpHK incorporated into antibodies with high efficiency and was available for maleimide conjugation or self-reaction depending on position in the amino acid sequence. CpHK at position K274 reacted with the maleimide drug-linker AZ1508 at a rate of ≈79 m^-1  s^-1 to produce functional antibody-drug conjugates (ADCs) in a one-step process. Incorporation of CpHK at position S239 resulted in dimerization, which covalently linked antibody heavy chains together. The diene ncAA described here is capable of producing therapeutic protein conjugates with clinically validated and widely available maleimide compounds, while also enabling proximity-based stapling through a DA dimerization reaction.

Preclinical evaluation of a GFRA1 targeted antibody-drug conjugate in breast cancer

Despite recent advances in treatment, breast cancer remains the second-most common cause of cancer death among American women. A greater understanding of the molecular characteristics of breast tumors could ultimately lead to improved tumor-targeted treatment options, particularly for subsets of breast cancer patients with unmet needs. Using an unbiased genomics approach to uncover membrane-localized tumor-associated antigens (TAAs), we have identified glial cell line derived neurotrophic factor (GDNF) family receptor α 1 (GFRA1) as a breast cancer TAA. Immunohistochemistry (IHC) revealed that GFRA1 displays a limited normal tissue expression profile coupled with overexpression in specific breast cancer subsets. The cell surface localization as determined by fluorescence-activated cell sorting (FACS) and the rapid internalization kinetics of GFRA1 makes it an ideal target for therapeutic exploitation as an antibody-drug conjugate (ADC). Here, we describe the development of a pyrrolobenzodiazepine (PBD)-armed, GFRA1-targeted ADC that demonstrates cytotoxicity in GFRA1-positive cell lines and patient-derived xenograft (PDX) models. The safety profile of the rat cross-reactive GFRA1-PBD was assessed in a rat toxicology study to find transient cellularity reductions in the bone marrow and peripheral blood, consistent with known off-target effects of PBD ADC's. These studies reveal no evidence of on-target toxicity and support further evaluation of GFRA1-PBD in GFRA1-positive tumors.

Pyrrolobenzodiazepine Antibody-Drug Conjugates Designed for Stable Thiol Conjugation

Thiosuccinimide-linked antibody-drug conjugates (ADCs) are susceptible to drug loss over time due to a retro-Michael reaction, which can be prevented by selecting stable conjugation positions or hydrolysis of the thiosuccinimide. Here, we investigate pyrrolobenzodiazepine (PBD) ADC drug-linkers equipped with N-phenyl maleimide functionality for stable thiol conjugation via thiosuccinimide hydrolysis. Two PBD drug-linker formats (enzyme-cleavable and non-cleavable) were evaluated following site-specific conjugation to an engineered cysteine incorporated at position T289, which is known to be unstable for N-alkyl maleimide conjugates. N-phenyl maleimide PBDs conjugated to antibodies with similar efficiencies as N-alkyl maleimide PBDs and enhanced thiosuccinimide hydrolysis for N-phenyl maleimide PBDs was confirmed by mass spectrometry, capillary isoelectric focusing, and a SYPRO Orange dye binding assay. All of the PBD ADCs were highly potent in vitro regardless of maleimide- or linker-type, exhibiting low pM EC₅₀ values. Thiol conjugation to N-phenyl maleimide PBD minimized the retro-Michael reaction in both rat and mouse serum. However, cleavage of the valine-alanine dipeptide in mouse serum for ADCs containing cleavable drug-linker led to drug loss regardless of maleimide type, which impacted ADC potency in tumor growth inhibition studies that were conducted in mouse models. Therapeutic improvement in mouse tumor models was realized for ADCs prepared with non-cleavable PBD drug-linkers that were conjugated through N-phenyl maleimide, where a stronger tumor growth inhibition (TGI) response was achieved when compared to the analogous N-alkyl maleimide drug-linker ADC. Altogether, our findings highlight the stability and efficacy benefits of N-phenyl maleimide functionality for ADCs that are produced with thiol-maleimide conjugation chemistry.

Vascular bursts enhance permeability of tumour blood vessels and improve nanoparticle delivery

Enhanced permeability in tumours is thought to result from malformed vascular walls with leaky cell-to-cell junctions. This assertion is backed by studies using electron microscopy and polymer casts that show incomplete pericyte coverage of tumour vessels and the presence of intercellular gaps. However, this gives the impression that tumour permeability is static amid a chaotic tumour environment. Using intravital confocal laser scanning microscopy we show that the permeability of tumour blood vessels includes a dynamic phenomenon characterized by vascular bursts followed by brief vigorous outward flow of fluid (named 'eruptions') into the tumour interstitial space. We propose that 'dynamic vents' form transient openings and closings at these leaky blood vessels. These stochastic eruptions may explain the enhanced extravasation of nanoparticles from the tumour blood vessels, and offer insights into the underlying distribution patterns of an administered drug.

A Nanoparticle Platform To Evaluate Bioconjugation and Receptor-Mediated Cell Uptake Using Cross-Linked Polyion Complex Micelles Bearing Antibody Fragments

Targeted nanomedicines are a promising technology for treatment of disease; however, preparation and characterization of well-defined protein-nanoparticle systems remain challenging. Here, we describe a platform technology to prepare antibody binding fragment (Fab)-bearing nanoparticles and an accompanying real-time cell-based assay to determine their cellular uptake compared to monoclonal antibodies (mAbs) and Fabs. The nanoparticle platform was composed of core-cross-linked polyion complex (PIC) micelles prepared from azide-functionalized PEG-b-poly(amino acids), that is, azido-PEG-b-poly(l-lysine) [N3-PEG-b-PLL] and azido-PEG-b-poly(aspartic acid) [N3-PEG-b-PAsp]. These PIC micelles were 30 nm in size and contained approximately 10 polymers per construct. Fabs were derived from an antibody binding the EphA2 receptor expressed on cancer cells and further engineered to contain a reactive cysteine for site-specific attachment and a cleavable His tag for purification from cell culture expression systems. Azide-functionalized micelles and thiol-containing Fab were linked using a heterobifunctional cross-linker (FPM-PEG4-DBCO) that contained a fluorophenyl-maleimide for stable conjugation to Fabs thiols and a strained alkyne (DBCO) group for coupling to micelle azide groups. Analysis of Fab-PIC micelle conjugates by fluorescence correlation spectroscopy, size exclusion chromatography, and UV-vis absorbance determined that each nanoparticle contained 2-3 Fabs. Evaluation of cellular uptake in receptor positive cancer cells by real-time fluorescence microscopy revealed that targeted Fab-PIC micelles achieved higher cell uptake than mAbs and Fabs, demonstrating the utility of this approach to identify targeted nanoparticle constructs with unique cellular internalization properties.

Live RB51 vaccine lyophilized hydrogel formulations with increased shelf life for practical ballistic delivery

Ballistic delivery capability is essential to delivering vaccines and other therapeutics effectively to both livestock and wildlife in many global scenarios. Here, lyophilized poly(ethylene glycol) (PEG)-glycolide dimethacrylate crosslinked but degradable hydrogels were assessed as payload vehicles to protect and deliver a viable bacterial vaccine, Brucella abortus strain RB51 (RB51), ballistically using commercial thermoplastic cellulosic degradable biobullets. Degradable PEG hydrogel rods loaded with ∼10(10) live RB51 bacteria (CFUs) were fabricated using three different polymerization methods, cut into fixed-sized payload segments, and lyophilized. Resulting dense, glassy RB51 vaccine-loaded monoliths were inserted into thermoplastic biobullet 100-μL payload chambers. Viability studies of lyophilized formulations assessed as a function of time and storage temperature supported the abilities of several conditions to produce acceptable vaccine shelf-lives. Fired from specifically designed air rifles, gel-loaded biobullets exhibit down-range ballistic properties (i.e., kinetic energy, trajectory, accuracy) similar to unloaded biobullets. Delivered to bovine tissue, these hydrogels rehydrate rapidly by swelling in tissue fluids, with complete hydration observed after 5h in serum. Live RB51 vaccine exhibited excellent viability following carrier polymerization, lyophilization, and storage, at levels sufficient for vaccine dosing to wild range bison, the intended target. These data validate lyophilized degradable PEG hydrogel rods as useful drug carriers for remote delivery of both live vaccines and other therapeutics to livestock, wildlife, or other free-range targets using ballistic technologies.

Stabilization of cysteine-linked antibody drug conjugates with N-aryl maleimides

Maleimides are often used to covalently attach drugs to cysteine thiols for production of antibody-drug conjugates (ADCs). However, ADCs formed with traditional N-alkyl maleimides have variable stability in the bloodstream leading to loss of drug. Here, we report that N-aryl maleimides form stable antibody conjugates under very mild conditions while also maintaining high conjugation efficiency. Thiol-maleimide coupling and ADC stabilization via thiosuccinimide hydrolysis were accelerated by addition of N-phenyl or N-fluorophenyl groups to the ring-head nitrogen. Cysteine-linked ADCs prepared with N-aryl maleimides exhibited less than 20% deconjugation in both thiol-containing buffer and serum when incubated at 37 °C over a period of 7 days, whereas the analogous ADCs prepared with N-alkyl maleimides showed 35-67% deconjugation under the same conditions. ADCs prepared with the anticancer drug N-phenyl maleimide monomethyl-auristatin-E (MMAE) maintained high cytotoxicity following long-term exposure to serum whereas the N-alkyl maleimide MMAE ADC lost potency over time. These data demonstrate that N-aryl maleimides are a convenient and flexible platform to improve the stability of ADCs through manipulation of functional groups attached to the maleimide ring-head nitrogen.

Precise engineering of siRNA delivery vehicles to tumors using polyion complexes and gold nanoparticles

For systemic delivery of siRNA to solid tumors, a size-regulated and reversibly stabilized nanoarchitecture was constructed by using a 20 kDa siRNA-loaded unimer polyion complex (uPIC) and 20 nm gold nanoparticle (AuNP). The uPIC was selectively prepared by charge-matched polyionic complexation of a poly(ethylene glycol)-b-poly(L-lysine) (PEG-PLL) copolymer bearing ∼40 positive charges (and thiol group at the ω-end) with a single siRNA bearing 40 negative charges. The thiol group at the ω-end of PEG-PLL further enabled successful conjugation of the uPICs onto the single AuNP through coordinate bonding, generating a nanoarchitecture (uPIC-AuNP) with a size of 38 nm and a narrow size distribution. In contrast, mixing thiolated PEG-PLLs and AuNPs produced a large aggregate in the absence of siRNA, suggesting the essential role of the preformed uPIC in the formation of nanoarchitecture. The smart uPIC-AuNPs were stable in serum-containing media and more resistant against heparin-induced counter polyanion exchange, compared to uPICs alone. On the other hand, the treatment of uPIC-AuNPs with an intracellular concentration of glutathione substantially compromised their stability and triggered the release of siRNA, demonstrating the reversible stability of these nanoarchitectures relative to thiol exchange and negatively charged AuNP surface. The uPIC-AuNPs efficiently delivered siRNA into cultured cancer cells, facilitating significant sequence-specific gene silencing without cytotoxicity. Systemically administered uPIC-AuNPs showed appreciably longer blood circulation time compared to controls, i.e., bare AuNPs and uPICs, indicating that the conjugation of uPICs onto AuNP was crucial for enhancing blood circulation time. Finally, the uPIC-AuNPs efficiently accumulated in a subcutaneously inoculated luciferase-expressing cervical cancer (HeLa-Luc) model and achieved significant luciferase gene silencing in the tumor tissue. These results demonstrate the strong potential of uPIC-AuNP nanoarchitectures for systemic siRNA delivery to solid tumors.

Actively-targeted polyion complex micelles stabilized by cholesterol and disulfide cross-linking for systemic delivery of siRNA to solid tumors

For small interfering RNA (siRNA)-based cancer therapies, we report an actively-targeted and stabilized polyion complex micelle designed to improve tumor accumulation and cancer cell uptake of siRNA following systemic administration. Improvement in micelle stability was achieved using two stabilization mechanisms; covalent disulfide cross-linking and non-covalent hydrophobic interactions. The polymer component was designed to provide disulfide cross-linking and cancer cell-targeting cyclic RGD peptide ligands, while cholesterol-modified siRNA (Chol-siRNA) provided additional hydrophobic stabilization to the micelle structure. Dynamic light scattering confirmed formation of nano-sized disulfide cross-linked micelles (<50 nm in diameter) with a narrow size distribution. Improved stability of Chol-siRNA-loaded micelles (Chol-siRNA micelles) was demonstrated by resistance to both the dilution in serum-containing medium and counter polyion exchange with dextran sulfate, compared to control micelles prepared with Chol-free siRNA (Chol-free micelles). Improved stability resulted in prolonged blood circulation time of Chol-siRNA micelles compared to Chol-free micelles. Furthermore, introduction of cRGD ligands onto Chol-siRNA micelles significantly facilitated accumulation of siRNA in a subcutaneous cervical cancer model following systemic administration. Ultimately, systemically administered cRGD/Chol-siRNA micelles exhibited significant gene silencing activity in the tumor, presumably due to their active targeting ability combined with the enhanced stability through both hydrophobic interactions of cholesterol and disulfide cross-linking.

Smart multilayered assembly for biocompatible siRNA delivery featuring dissolvable silica, endosome-disrupting polycation, and detachable PEG

Multifunctional delivery systems of small interfering RNA (siRNA) are needed to overcome the intrinsic biological barriers toward efficient gene silencing in the cell cytoplasm. In this report, a smart multilayered assembly (SMA) was fabricated by a layer-by-layer method with polyionic materials. The SMA was designed to feature a siRNA-loaded core, a transiently core-stabilizing silica interlayer, an endosome-disrupting polycation interlayer, and a biocompatible poly(ethylene glycol) (PEG) shell with reductive environment-responsive detachability. The SMA was confirmed to be approximately 160 nm in size with narrow distribution and spherical morphology by DLS and TEM analyses. The PEG detachability of the SMA based on disulfide cleavage was also confirmed by the increase in both ζ-potential and size due to the exposure of the polycation interlayer and the compromised colloidal stability. The silica interlayer rendered the SMA highly tolerant to dissociation induced by anionic lipids, while after 24 h dialysis siRNA release from the SMA was clearly observed, presumably due to gradual dissolution of the silica interlayer based on the equilibrium shift to silicate ions. The entrapment ratio of siRNA delivered by the SMA within the endosome was significantly lower than that by nondisulfide control (NDC) without PEG detachability, suggesting the improved endosomal escape of SMA with the exposed, endosome-disrupting interlayer after PEG detachment. SMAs induced significantly higher gene silencing efficiency in various cultured cells, compared to NDC, without associated cytotoxicity. The systemic administration of SMAs for subcutaneous tumor-bearing mice achieved significant endogenous gene silencing in tumor tissue without hematological toxicity.

Targeted polymeric micelles for siRNA treatment of experimental cancer by intravenous injection

Small interfering ribonucleic acid (siRNA) cancer therapies administered by intravenous injection require a delivery system for transport from the bloodstream into the cytoplasm of diseased cells to perform the function of gene silencing. Here we describe nanosized polymeric micelles that deliver siRNA to solid tumors and elicit a therapeutic effect. Stable multifunctional micelle structures on the order of 45 nm in size formed by spontaneous self-assembly of block copolymers with siRNA. Block copolymers used for micelle formation were designed and synthesized to contain three main features: a siRNA binding segment containing thiols, a hydrophilic nonbinding segment, and a cell-surface binding peptide. Specifically, poly(ethylene glycol)-block-poly(L-lysine) (PEG-b-PLL) comprising lysine amines modified with 2-iminothiolane (2IT) and the cyclo-Arg-Gly-Asp (cRGD) peptide on the PEG terminus was used. Modification of PEG-b-PLL with 2IT led to improved control of micelle formation and also increased stability in the blood compartment, while installation of the cRGD peptide improved biological activity. Incorporation of siRNA into stable micelle structures containing the cRGD peptide resulted in increased gene silencing ability, improved cell uptake, and broader subcellular distribution in vitro and also improved accumulation in both the tumor mass and tumor-associated blood vessels following intravenous injection into mice. Furthermore, stable and targeted micelles inhibited the growth of subcutaneous HeLa tumor models and demonstrated gene silencing in the tumor mass following treatment with antiangiogenic siRNAs. This new micellar nanomedicine could potentially expand the utility of siRNA-based therapies for cancer treatments that require intravenous injection.

Pancreatic cancer therapy by systemic administration of VEGF siRNA contained in calcium phosphate/charge-conversional polymer hybrid nanoparticles

Development of an efficient in vivo delivery vehicle of small interfering RNA (siRNA) is the key challenge for successful siRNA-based therapies. In this study, toward systemic delivery of siRNA to solid tumors, a smart polymer/calcium phosphate (CaP)/siRNA hybrid nanoparticle was prepared to feature biocompatibility, reversible stability and endosomal escape functionality using a pH sensitive block copolymer of poly(ethylene glycol) and charge-conversional polymer (PEG-CCP), of which anionic functional groups could be converted to cationic groups in an endosomal acidic condition for facilitated endosomal escape. Nanoparticles were confirmed to be approximately 100nm in size, narrowly dispersed and spherical. Also, the nanoparticle was highly tolerable in medium containing serum, while releasing the entrapped siRNA in a cytoplasm-mimicking ionic condition, presumably based on the equilibrium between CaP complexes and calcium ions. Further, the nanoparticle showed high gene silencing efficiency in cultured pancreatic cancer cells (BxPC3) without associated cytotoxicity. Ultimately, systemic administration of the nanoparticles carrying vascular endothelium growth factor (VEGF) siRNA led to the significant reduction in the subcutaneous BxPC3 tumor growth, well consistent with the enhanced accumulation of siRNA and the significant VEGF gene silencing (~68%) in the tumor. Thus, the hybrid nanoparticle was demonstrated to be a promising formulation toward siRNA-based cancer therapies.

Photosensitisation, crystal-associated cholangiohepatopathy, and acute renal tubular necrosis in calves following ingestion of Phytolacca octandra (inkweed)

CASE HISTORY

In March 2006, an outbreak of photosensitivity affecting 6-8-month-old Friesian heifer calves on a farm in the Rangitikei district of New Zealand was investigated. The calves were grazing wheat stubble paddocks that also had a variety of weeds, especially Phytolacca octandra (inkweed). They also had access to pond water that contained potentially toxic concentrations of the cyanobacteria (blue-green algae) Microcystis and Planktothrix spp.

CLINICAL FINDINGS

Initially, affected animals showed acute irritation, agitation, reluctance to walk, recumbency in some animals, hyperaemia of unpigmented skin and jaundice. Serum chemistry revealed elevated liver enzyme activities and azotaemia. Later in the outbreak, exudative dermatitis with formation of crusts on unpigmented skin, dehydration and inappetence were notable signs, as well as occasional diarrhoea. PATHOLOGICAL AND TOXICOLOGICAL FINDINGS: Post-mortem examinations following euthanasia of four severely affected calves and a fifth animal that died naturally revealed livers that were grossly orange brown and mildly enlarged, and kidneys that were enlarged and pale brown. Microscopic lesions in the liver were mild; however, small birefringent crystals in the bile ducts were noted in the first two cases. In contrast, renal lesions were moderate to severe, and included prominent segmental tubular necrosis, granular and cellular casts, and mild interstitial non-suppurative inflammation. In the kidneys of animals examined later in the outbreak, there was early interstitial fibrosis as well as tubular regeneration, with numerous hyaline casts in the renal medulla. Inkweed plants had been heavily browsed, and recognisable portions of the plant were found in the gastrointestinal tracts of affected calves. Chemical analysis of inkweed material revealed triterpene saponins. No known hepatotoxic or nephrotoxic plants were identified in the paddocks. The hepatic lesions were not consistent with published descriptions of cyanobacterial toxicity. Sporidesmin toxicity was ruled out.

DIAGNOSIS

Hepatogenous photosensitivity, crystal-associated cholangiohepatopathy, toxic acute renal tubular necrosis, associated with the ingestion of P. octandra, and possibly complicated by cyanobacteria in the water.

CLINICAL RELEVANCE

Crystal-associated cholangiohepatopathy with photosensitivity in cattle is rare, and has only been reported in steroidal saponin-containing Brachiaria decumbens poisoning, in Brazil. The consistent pattern of toxic acute renal tubular necrosis was similar to that caused by the ingestion of Quercus, Amaranthus or Lantana spp. A combination of toxicities was conceivable but circumstantial evidence strongly implicated P. octandra. Further toxicological investigation of this plant is warranted before it can be listed as a known nephrotoxin of cattle.

Comparison of hydrazone heterobifunctional cross-linking agents for reversible conjugation of thiol-containing chemistry

Reversible covalent conjugation chemistries that allow site- and condition-specific coupling and uncoupling reactions are attractive components in nanotechnologies, bioconjugation methods, imaging, and drug delivery systems. Here, we compare three heterobifunctional cross-linkers, containing both thiol- and amine-reactive chemistries, to form pH-labile hydrazones with hydrazide derivatives of the known and often published water-soluble polymer, poly[N-(2-hydroxypropyl methacrylamide)] (pHPMA), while subsequently coupling thiol-containing molecules to the cross-linker via maleimide addition. Two novel cross-linkers were prepared from the popular heterobifunctional cross-linking agent, succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC), modified to contain either terminal aldehyde groups (i.e., 1-(N-3-propanal)-4-(N-maleimidomethyl) cyclohexane carboxamide, PMCA) or methylketone groups (i.e., 1-(N-3-butanone)-4-(N-maleimidomethyl) cyclohexane carboxamide, BMCA). A third cross-linking agent was the commercially available N-4-acetylphenyl maleimide (APM). PMCA and BMCA exhibited excellent reactivity toward hydrazide-derivatized pHPMA with essentially complete hydrazone conjugation to polymer reactive sites, while APM coupled only ∼60% of available reactive sites on the polymer despite a 3-fold molar excess relative to polymer hydrazide groups. All polymer hydrazone conjugates bearing these bifunctional agents were then further reacted with thiol-modified tetramethylrhodamine dye, confirming cross-linker maleimide reactivity after initial hydrazone polymer conjugation. Incubation of dye-labeled polymer conjugates in phosphate buffered saline at 37 °C showed that hydrazone coupling resulting from APM exhibited the greatest difference in stability between pH 7.4 and 5.0, with hydrolysis and dye release increased at pH 5.0 over a 24 h incubation period. Polymer conjugates bearing hydrazones formed from cross-linker BMCA exhibited intermediate stability with hydrolysis much greater at pH 5.0 at early time points, but hydrolysis at pH 7.4 was significant after 5 h. Hydrazones formed with the PMCA cross-linker showed no difference in release rates at pH 7.4 and 5.0.

Direct and instantaneous observation of intravenously injected substances using intravital confocal micro-videography

We describe the development and application of intravital confocal micro-videography to visualize entrance, distribution, and clearance of drugs within various tissues and organs. We use a Nikon A1R confocal laser scanning microscope system attached to an upright ECLIPSE FN1. The Nikon A1R allows simultaneous four channel acquisition and speed of 30 frames per second while maintaining high resolution of 512 × 512 scanned points. The key techniques of our intravital imaging are (1) to present a flat and perpendicular surface to the objective lens, and (2) to expose the subject with little or no bleeding to facilitate optical access to multiple tissues and organs, and (3) to isolate the subject from the body movement without compressing the blood vessels, and (4) to insert a tail vein catheter for timed injection without moving the subject. Ear lobe dermis tissue was accessible without surgery. Liver, kidney, and subcutaneous tumor were accessed following exteriorization through skin incision. In order to image initial extravasations of compounds into tissue following intravenous injection, movie acquisition was initialized prior to drug administration. Our technique can serve as a powerful tool for investigating biological mechanisms and functions of intravenously injected drugs, with both spatial and temporal resolution.

Polyplex micelles prepared from ω-cholesteryl PEG-polycation block copolymers for systemic gene delivery

Polyplex micelles formed with plasmid DNA (pDNA) and poly(ethylene glycol) (PEG)-block-poly{N-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} [PAsp(DET)] exhibit effective endosomal escaping properties based on di-protonation of diamine side chains with decreasing pH, which improves their transfection efficiency and thus are promising candidates for local in vivo gene transfer. Here, PEG-PAsp(DET) polyplex micelles were further improved as in vivo systemic vectors by introduction of cholesterol (Chole) into the ω-terminus of PEG-PAsp(DET) to obtain PEG-PAsp(DET)-Chole. Introduction of the cholesterol resulted in enhanced association of block copolymers with pDNA, which led to increased stability in proteinous medium and also in the blood stream after systemic injection compared to PEG-PAsp(DET) micelles. The synergistic effect between enhanced polymer association with pDNA and increased micelle stability of PEG-PAsp(DET)-Chole polyplex micelles led to high in vitro gene transfer even at relatively low concentrations, due to efficient cellular uptake and effective endosomal escape of block copolymers and pDNA. Finally, PEG-PAsp(DET)-Chole micelles achieved significant suppression of tumor growth following intravenous injection into mice bearing a subcutaneous pancreatic tumor using therapeutic pDNA encoding an anti-angiogenic protein. These results suggest that PEG-PAsp(DET)-Chole micelles can be effective systemic gene vectors for treatment of solid tumors.

Optical properties and application of a reactive and bioreducible thiol-containing tetramethylrhodamine dimer

Thiolated dimeric tetramethylrhodamine (TAMRA) was synthesized in a straightforward procedure utilizing commercially available 5(6)-succinimidyl TAMRA and cystamine hydrochloride. The thiol-containing TAMRA dimer displayed distinct spectral properties in reduced and oxidized forms; covalent dimer formation produced greater effects on the spectral properties than previously reported for noncovalent TAMRA dimers or dimers formed with shorter carbon spacers. The resulting TAMRA disulfide dimer exhibited a hypsochromic shift of 34 nm relative to the reduced monomer species and an isosbestic point at 532 nm between reduced monomeric and oxidized dimeric forms. Molar extinction coefficients of the monomer and dimer relative to moles of TAMRA were similar (6.61 x 10(4) M(-1) cm(-1) and 6.42 x 10(-4) M(-1) cm(-1), respectively). However, fluorescence emission was altered with >93% of dye fluorescence quenched in phosphate buffered saline upon dimer formation. A 520:554 nm absorbance intensity ratio of 2.64 was observed for the oxidized ssTAMRA dimer, almost twice as high as values reported for noncovalent TAMRA dimers. The resulting disulfide dye was easily reduced using both soluble and agarose gel immobilized tris(2-carboxyethyl) phosphine and fresh cell lysate from cultured RAW 264.7 macrophage cells. Absorbance intensity ratios at 554 and 520 nm were used to determine the oxidation half-life of a 1.2 x 10(-5) M solution of reduced TAMRA stored in ambient atmosphere to be approximately 50 h at 22 degrees C. The free thiol dye was further reacted with maleimide-derivatized poly(hydroxypropyl methacrylamide) to yield the dye-labeled polymer conjugate. This dye derivative should prove useful as a dithiol reduction-sensitive fluorescent probe in cellular tracking systems, as well as a thiol-based dye-labeling reagent due to its easy preparation from readily available materials, environmental sensitivity, and simple activation to produce distinct spectral states. The enhanced spectral properties of the covalent TAMRA dimer described here could be useful to prepare more advanced reporter molecules and bioconjugates.

Delivering the code: polyplex carriers for deoxyribonucleic acid and ribonucleic acid interference therapies

Nucleic acid-based therapies offer great potential for treatment of a variety of diseases including cancer by modulating protein expression with DNA or small interfering RNA. However, realization of their full therapeutic potential is currently limited due to an inability to reach the target site in an active form. Identification of delivery barriers such as stability in circulation, resistance to degradation and entrapment in subcellular vesicles has led to development of sophisticated multifunctional synthetic polymers for forming ionic complexes with nucleic acids and also providing performance-enhancing features. The most promising designs comprise features to help increase stability in circulation and also contain functionality to aid in endosome escape of nucleic acid cargo after cellular internalization.

Polymeric micelles from poly(ethylene glycol)-poly(amino acid) block copolymer for drug and gene delivery

Dramatic advances in biological research have revealed the mechanisms underlying many diseases at the molecular level. However, conventional techniques may be inadequate for direct application of this new knowledge to medical treatments. Nanobiotechnology, which integrates biology with the rapidly growing field of nanotechnology, has great potential to overcome many technical problems and lead to the development of effective therapies. The use of nanobiotechnology in drug delivery systems (DDS) is attractive for advanced treatment of conditions such as cancer and genetic diseases. In this review paper for a special issue on biomaterial research in Japan, we discuss the development of DDS based on polymeric micelles mainly in our group for anti-cancer drug and gene delivery, and also address our challenges associated with developing polymeric micelles as super-functionalized nanodevices with intelligent performance.

Environment-responsive block copolymer micelles with a disulfide cross-linked core for enhanced siRNA delivery

A core-shell-type polyion complex (PIC) micelle with a disulfide cross-linked core was prepared through the assembly of iminothiolane-modified poly(ethylene glycol)-block-poly(L-lysine) [PEG-b-(PLL-IM)] and siRNA at a characteristic optimum mixing ratio. The PIC micelles showed a spherical shape of approximately 60 nm in diameter with a narrow distribution. The micellar structure was maintained at physiological ionic strength but was disrupted under reductive conditions because of the cleavage of disulfide cross-links, which is desirable for siRNA release in the intracellular reductive environment. Importantly, environment-responsive PIC micelles achieved 100-fold higher siRNA transfection efficacy compared with non-cross-linked PICs prepared from PEG-b-poly(L-lysine), which were not stable at physiological ionic strength. PICs formed with PEG-b-(PLL-IM) at nonoptimum ratios did not assemble into micellar structure and did not achieve gene silencing following siRNA transfection. These findings show the feasibility of core cross-linked PIC micelles as carriers for therapeutic siRNA and show that stable micellar structure is critical for effective siRNA delivery into target cells.

Photopolymerized hydrogel carriers for live vaccine ballistic delivery

Photopolymerized poly(ethylene glycol) (PEG)-crosslinked hydrogels were assessed for their ability to serve as a payload vehicle to deliver a viable bacterial vaccine (Brucella abortus strain RB51 (RB51) to bison in Yellowstone National Park) ballistically using thermoplastic degradable Biobullets. PEG modified with degradable glycolide or lactide oligomers capped with photopolymerizable methacrylate groups served to crosslink the hydrogel vaccine carrier inside commercial hydroxypropylcellulose Biobullets. Release of 1 microm diameter model fluorescent particles from hydrogels followed known degradation trends for glycolide- and lactide-modified PEG hydrogels. All particles were released from PEG-co-glycolide hydrogels after approximately 10 days and PEG-co-lactide hydrogels after approximately 45 days following gel degradation. Minimal particle release was observed from pure PEG dimethacrylate hydrogels over 40 days. P. aeruginosa (strain PAO1) and RB51 live vaccines exhibit excellent viability following exposure to photopolymerization encapsulation within these gel matrices. Hydrogels photopolymerized into the payload chamber of Biobullets exhibit similar ballistic properties to commercially available Biobullets and penetrate and remain intact when fired intramuscularly into live elk for release of their gel payload in the host.

Immunologic responses of bison to vaccination with Brucella abortus strain RB51: comparison of parenteral to ballistic delivery via compressed pellets or photopolymerized hydrogels

This study compared responses of bison calves to 10(10)CFU of Brucella abortus strain RB51 (SRB51) delivered by parenteral or ballistic methods. Two types of biobullet payloads were evaluated; compacted SRB51 pellets or SRB51 encapsulated in photopolymerized poly(ethylene glycol) hydrogels. Bison were vaccinated with saline, parenteral SRB51 alone, or in combination with Spirovac, or ballistically with compressed SRB51 or hydrogel biobullets. Bison parenterally vaccinated with SRB51 had greater (P<0.05) immunologic responses when compared to control bison. Co-administration of Spirovac as an adjuvant did not influence immunologic responses. As compared to compressed SRB51 biobullets, ballistic vaccination with hydrogel biobullets increased cellular immune responses at some sampling times. Our data suggest that hydrogel formulations of SRB51 may be a superior alternative to compressed SRB51 tablets for ballistic vaccination of bison. Although preliminary, data suggests that immunologic responses of bison to SRB51 hydrogel bullets are similar to responses after parenteral vaccination with SRB51.

Design and synthesis of a new polymer drug delivery conjugate

This work describes the design and synthesis of a novel polymer conjugate to facilitate intracellular release of attached cargo. Water soluble poly[N(2-hydroxypropyl) methacrylamide] with derivatizable pendant side chains was used as the polymer carrier. The membrane active Tat peptide was masked with poly(ethylene glycol) to inhibit non-specific interactions with exterior cell membranes, and then covalently linked to poly[N-(2-hydroxypropyl) methacrylamide]. A novel heterobifunctional crosslinker was synthesized containing both maleimide and aldehyde functionality to allow attachment of peptides to the polymer backbone through a pH sensitive bond. Analysis of the proposed conjugate by gel permeation chromatography, nuclear absorbance spectroscopy, and absorbance measurements indicate that the desired compound has been synthesized.

Design strategies to improve soluble macromolecular delivery constructs

Macromolecular therapeutics provide numerous benefits for the delivery of cytotoxic or poorly soluble drugs in vivo. However, these constructs often encounter barriers for drug delivery on both the systemic and subcellular level. Many soluble polymer carriers have been designed to surmount specific physiological barriers individually, but less work has been dedicated to designing an all-encompassing construct that addresses multiple therapeutic barriers at once. Incorporation of multiple agents already individually known to increase effectiveness into one carrier could further improve current drug delivery technology. Recent developments in subcellular delivery of therapeutic agents in soluble macromolecular carriers are discussed in the context of the future possibility for the design of an all-encompassing soluble multi-functional drug delivery vehicle.

Mechanical ventilation in hematopoietic stem cell transplantation: can We effectively predict outcomes?

BACKGROUND

Survival rates from mechanical ventilation (MV) in allogeneic bone marrow transplantation are poor, but little is known about the need for and outcomes from MV in patients who undergo autologous hematopoietic stem cell transplantation (AHSCT).

STUDY OBJECTIVE

To determine the frequency of and risk factors for the use of MV in recipients of AHSCT and to identify predictors of survival in mechanically ventilated AHSCT patients.

DESIGN

Retrospective, cohort analysis

SETTING

Tertiary-care, university-affiliated medical center.

PATIENTS

One hundred fifty-nine consecutive patients who underwent AHSCT.

INTERVENTIONS

Patient surveillance and data collection.

MEASUREMENTS AND RESULTS

The primary outcome measure was the need for MV, and the secondary end point was survival after MV. Of 159 patients, 17 required MV (10. 7%). Three variables were associated with the need for MV: increasing age, use of total body irradiation in the conditioning regimen, and treatment with amphotericin B. As a screening test to predict the need for MV, no risk factor had a sensitivity or specificity > 82%. Three of the 17 mechanically ventilated patients (17.6%) survived to discharge. Only the mean APACHE (acute physiology and chronic health evaluation) II score separated survivors from nonsurvivors (21.7 vs 31.4; p = 0.029). Both the duration of MV and the length of stay in the ICU were similar in survivors and nonsurvivors.

CONCLUSIONS

We conclude that MV is infrequently needed following AHSCT. Although survival after MV in these patients is limited, clinical variables do not reliably allow clinicians to prospectively identify patients destined to die.

A survey method for investigating ethical decision making in family practice

BACKGROUND

The tension between respect for patient autonomy versus concern for patient welfare is a challenging ethical issue for physicians. The purpose of this research was to describe a method for analyzing ethical decisions and to report the results of a survey of ethical decision making among family physicians.

METHODS

We developed a survey instrument that used simulated case scenarios, each of which posed an ethical dilemma. The ethical problems on the survey included the extent to which diagnostic information should be revealed to patients, the extent to which physicians should become involved in patients' life-style issues, and how to deal with patients' family problems. We mailed the questionnaire to 1,300 US family physicians.

RESULTS

Six hundred seventy-four physicians responded. Respondents did not deal with the simulated ethical problems in a uniform manner and often tended to respond more to specific details of a case rather than the overall ethical dilemma posed. Physicians who chose a course of action giving patients more control were motivated by factors that showed respect for patient autonomy. On the other hand, physicians who chose a course of action giving patients less control were not motivated by factors suggesting a concern for patient welfare.

CONCLUSIONS

Based on responses to simulated case scenarios, family physicians did not demonstrate a uniform approach but rather a more contextual one. Respect for patient autonomy was linked to family physicians' reported courses of action.

Ethical decision making by family doctors in Canada, Britain and the United States

Family doctors in Canada and the U.S. and general practitioners in England and Wales were sent a questionnaire containing six cases that raised moral issues. The doctors were asked to select the most appropriate course of action for each case as well as reasons for that decision. The ethical problems concerned how much information to divulge to patients, how extensively a physician should become involved in the lifestyles of patients, and how to deal with a possible family problem. The respondents selected different courses of action for the cases. More U.S. than Canadian or British physicians chose to divulge information, while more British than Canadian or U.S. physicians chose not to become involved in patients' lifestyles. Physicians who chose to divulge information were likely to be young, male, live in a small community, and have no academic affiliation. Physicians who chose not to become involved in lifestyle issues were likely to be young, church attenders, and in group practice in a small community.

Ethical decision making by British general practitioners

General practitioners in England and Wales were sent a questionnaire asking how they would handle the ethical problems posed by six case vignettes and their reasons for their decisions. The ethical problems included: how much information to divulge to patients, how extensively a physician should become involved in the lifestyles of patients and how to deal with a possible family problem. The varying patterns of response to the six cases suggested that ethical issues are resolved in a case-by-case, not a theoretical, basis.

Meperidine and normeperidine distribution in the rhesus monkey

Previous work has shown that both meperidine and normeperidine are transferred across the placenta to the fetus. Little is known in primates, however, about the tissue deposition of these compounds. Four pregnant, dated rhesus monkeys within one week of term were anesthetized for cesarean delivery. An equal mixture of meperidine and normeperidine was administered as an intravenous bolus 10 minutes before delivery (1.25 mg/kg). The infants were then sacrificed at 20 minutes after birth and the concentration of the compounds in various organ systems were analyzed by gas-liquid chromatography and mass spectroscopy (GLC-MS). The infant serum 20 minutes after delivery revealed a meperidine concentration of 2.23 micrograms/ml and a normeperidine level of 0.67 micrograms/ml (3:1). In contrast, the tissues analyzed showed a much higher concentration of the metabolite in the liver (1:7), gallbladder (1:3), and brain (1:2). Other tissues, such as muscle and kidney, demonstrated equal levels of the two compounds. The authors conclude that normeperidine is quickly transferred to fetal tissues and to a greater degree than the parent compound in certain organs. The increased distribution, particularly in the brain, could account for the toxic actions in the cerebrum of the derivatives of meperidine.

Ethical decision making by Canadian family physicians

Canadian family physicians were sent questionnaires that asked how they would handle the ethical problems posed by six sample cases and what reasons were relevant to their decisions. The ethical problems concerned how much information to divulge to patients, how extensively a physician should become involved in the lifestyles of patients and how to deal with a possible family problem. The study identified characteristics of family physicians that affect their ethical decision making and tested a theoretical model that regards ethical problems as conflicts between respecting patient autonomy and promoting patient welfare. The varied responses suggested that ethical issues are resolved on a case-by-case, rather than a theoretical, basis. Certification in family medicine was the only characteristic associated with a consistent pattern of responses; certificants were more likely than other physicians to involve patients in decisions.

Meperidine and normeperidine metabolism in the rhesus monkey

Meperidine and its principle metabolite, normeperidine, were given intravenously to four non-human primates prior to cesarean delivery in an equivalent dose for human parturients. The status of the infants regarding neonatal depression was assessed at delivery. Repeated blood samples from both the mother and the neonate were obtained over a period of 4 days. The levels of meperidine and normeperidine were analyzed. The results showed that the metabolism of meperidine and normeperidine in the non-human primate was essentially the same as that observed in the human parturient. In addition, normeperidine appeared to be more toxic than meperidine to the neonate. Finally, there does not appear to be an evidence for neonatal metabolism of meperidine to normeperidine.

Sex and the mentally retarded: is sterilization the answer?

The sexuality of the mentally handicapped concerns them, their parents, their family physicians and other health professionals. Parents need advice, and the well-informed family physician who has the family's trust is in a good position to give it. However, the physician must protect the rights and autonomy of the mentally handicapped patient concerning contraception, surgical sterilization and hysterectomy. Before recommending a method of contraception, the physician must identify any medical risks and be satisfied that the patient clearly understands risks and advantages. Sterilization as a method of contraception should never be considered unless the patient chooses it; involuntary sterilization can produce serious and significant psychological damage. The physician must give a detailed explanation to make sure the patient electing to be surgically sterilized understands the procedure and has fully consented without coercion. Hysterectomy should never be used as a method of sterilization.