Pharmacokinetics and tissue distribution of cisplatin and conjugates of cisplatin with carboxymethyldextran and A5B7 monoclonal antibody in CD1 mice

Efficacy, Pharmacokinetics, and Toxicity Profiles of a Broad Anti-SARS-CoV-2 Neutralizing Antibody

We recently reported the isolation and characterization of an anti-SARS-CoV-2 antibody, called IgG-A7, that protects transgenic mice expressing the human angiotensin-converting enzyme 2 (hACE-2) from an infection with SARS-CoV-2 Wuhan. We show here that IgG-A7 protected 100% of the transgenic mice infected with Delta (B.1.617.2) and Omicron (B.1.1.529) at doses of 0.5 and 5 mg/kg, respectively. In addition, we studied the pharmacokinetic (PK) profile and toxicology (Tox) of IgG-A7 in CD-1 mice at single doses of 100 and 200 mg/kg. The PK parameters at these high doses were proportional to the doses, with serum half-life of ~10.5 days. IgG-A7 was well tolerated with no signs of toxicity in urine and blood samples, nor in histopathology analyses. Tissue cross-reactivity (TCR) with a panel of mouse and human tissues showed no evidence of IgG-A7 interaction with the tissues of these species, supporting the PK/Tox results and suggesting that, while IgG-A7 has a broad efficacy profile, it is not toxic in humans. Thus, the information generated in the CD-1 mice as a PK/Tox model complemented with the mouse and human TCR, could be of relevance as an alternative to Non-Human Primates (NHPs) in rapidly emerging viral diseases and/or quickly evolving viruses such as SARS-CoV-2.

Determining the Potential of DNA Damage Response (DDR) Inhibitors in Cervical Cancer Therapy

Cisplatin-based chemo-radiotherapy (CRT) is the standard treatment for advanced cervical cancer (CC) but the response rate is poor (46-72%) and cisplatin is nephrotoxic. Therefore, better treatment of CC is urgently needed. We have directly compared, for the first time, the cytotoxicity of four DDR inhibitors (rucaparib/PARPi, VE-821/ATRi, PF-477736/CHK1i and MK-1775/WEE1i) as single agents, and in combination with cisplatin and radiotherapy (RT) in a panel of CC cells. All inhibitors alone caused concentration-dependent cytotoxicity. Low ATM and DNA-PKcs levels were associated with greater VE-821 cytotoxicity. Cisplatin induced ATR, CHK1 and WEE1 activity in all of the cell lines. Cisplatin only activated PARP in S-phase cells, but RT activated PARP in the entire population. Rucaparib was the most potent radiosensitiser and VE-821 was the most potent chemosensitiser. VE-821, PF-47736 and MK-1775 attenuated cisplatin-induced S-phase arrest but tended to increase G2 phase accumulation. In mice, cisplatin-induced acute kidney injury was associated with oxidative stress and PARP activation and was prevented by rucaparib. Therefore, while all inhibitors investigated may increase the efficacy of CRT, the greatest clinical potential of rucaparib may be in limiting kidney damage, which is dose-limiting.

Facile protein conjugation of platinum for light-activated cytotoxic payload release

The novel Pt(iv) complex trans,trans-[Pt(N3)2(Py)2(OH)(OCO-(PEG)2-NHCSNH-Ph-NCS)] (Pt4) conjugates to the side chain of lysine amino acids in proteins under mild conditions. Reaction with myoglobin generated a bioconjugate that was stable in the dark, but released a Pt(iv) prodrug upon visible light irradiation. A similar procedure was used to conjugate Pt4 to the antibody trastuzumab, resulting in the first photoactivatable Pt(iv)-antibody conjugate, demonstrating potential for highly selective cancer phototherapy.

Hypoxia-responsive nanoparticle based drug delivery systems in cancer therapy: An up-to-date review

Hypoxia is a salient feature observed in most solid malignancies that holds a pivotal role in angiogenesis, metastasis and resistance to conventional cancer therapeutic approaches, and thus enables cancer progression. However, the typical characteristics of hypoxic cells such as low oxygen levels and highly bio-reductive environment can offer stimuli-responsive drug release to aid in tumor-specific chemo, radio, photodyanamic and sonodynamic therapies. This approach based on targeting the poorly oxygenated tumor habitats offers the prospective to overcome the difficulties that arises due to heterogenic nature of tumor and could be possibly used in the design of diagnostic as well as therapeutic nanocarriers for targeting various types of solid cancers. Consequently, hypoxia triggered nanoparticle based drug delivery systems is a rapidly progressing research area in developing effective strategies to combat drug-resistance in solid tumors. The present review presents the recent advances in the development of hypoxia-responsive nanovehicles for drug delivery to heterogeneous tumors. The initial sections of the article provides insights into the development of hypoxia in growing cancer and its role in disease progression. The current limitations and the future prospective of hypoxia-stimulated nanomachines for cancer treatment are also discussed.

Metal-based antibody drug conjugates. Potential and challenges in their application as targeted therapies in cancer

Antibody drug conjugates have emerged as a very attractive type of targeted therapy in cancer. They combine the antigen-targeting specificity of monoclonal antibodies (mAbs) with the cytotoxic potency of chemotherapeutics. This review focuses on antibody drug conjugates based on metal-containing cytotoxic payloads. We will also describe antibody drug conjugates (ADCs) in which a metal-based component (mostly metallic nanoparticles) exerts a relevant function in the ADC (for photodynamic or photothermal therapy, as air-plasma-enhancer or chemo-sensitizer, as carrier of other cytotoxic payloads or as an integral part of the linker structure). Challenges and opportunities to increase the translational potential of these ADCs will be discussed.

Trastuzumab gold-conjugates: synthetic approach and in vitro evaluation of anticancer activities in breast cancer cell lines

We describe the preparation of gold(i)-compounds that are amenable to efficient bioconjugation with monoclonal antibodies via activated ester or maleimide linkers. New Trastuzumab-gold conjugates were synthesized and fully characterized. These bioconjugates are significantly more cytotoxic (sub-micromolar range) to HER2-positive breast cancer cells than the gold complexes and Trastuzumab.

Water-soluble metalloporphyrinates with excellent photo-induced anticancer activity resulting from high tumor accumulation

To develop a water-soluble and tumor-targeted photosensitizer for photodynamic therapy (PDT), a porphyrin framework containing the metal ion gallium(III) was combined with platinum(II)-based groups to produce two new pentacationic metalloporphyrinates, Ga-4cisPtTPyP (5,10,15,20-tetrakis{cis-diammine-chloro-platinum(II)}(4-pyridyl)-porphyrinato gallium(III) hydroxide tetranitrate) and Ga-4transPtTPyP (5,10,15,20-tetrakis{trans-diammine-chloro-platinum(II)} (4-pyridyl)-porphyrinato gallium(III) hydroxide tetranitrate). Both complexes exhibited high singlet oxygen quantum yields (Φ_∆) and remarkable photocytotoxicity with appreciable phototoxic indexes (PIs). In particular, Ga-4cisPtTPyP showed a low IC₅₀ value (Colon 26: 0.12μM; Sarcoma 180: 0.08μM) under illumination and its PI up to 1000. With outstanding tumor accumulation (tumor/muscle ratio>9), Ga-4cisPtTPyP almost completely inhibited tumor growth over two weeks in an in vivo PDT assay. These results imply that Ga-4cisPtTPyP could be a promising anticancer agent for use in PDT.

Enhancement of anti-tumor activity of hybrid peptide in conjugation with carboxymethyl dextran via disulfide linkers

To improve the anti-tumor activity of EGFR2R-lytic hybrid peptide, we prepared peptide-modified dextran conjugates with the disulfide bonds between thiolated carboxymethyl dextran (CMD-Cys) and cysteine-conjugated peptide (EGFR2R-lytic-Cys). In vitro release studies showed that the peptide was released from the CMD-s-s-peptide conjugate in a concentration-dependent manner in the presence of glutathione (GSH, 2μM-2mM). The CMD-s-s-peptide conjugate exhibited a similar cytotoxic activity with free peptide alone against human pancreatic cancer BxPC-3 cells in vitro. Furthermore, it was shown that the CMD-s-s-peptide conjugates were highly accumulated in tumor tissue in a mouse xenograft model using BxPC-3 cells, and the anti-tumor activity of the conjugate was more effective than that of the free peptide. In addition, the plasma concentrations of peptide were moderately increased and the elimination half-life of the peptide was prolonged after intravenous injection of CMD-s-s-peptide conjugates. These results demonstrated that the conjugate based on thiolated CMD polymer would be potentially useful carriers for the sustained release of the hybrid peptide in vivo.

Bioreducible carboxymethyl dextran nanoparticles for tumor-targeted drug delivery

Bioreducible carboxymethyl dextran (CMD) derivatives are synthesized by the chemical modification of CMD with lithocholic acid (LCA) through a disulfide linkage. The hydrophobic nature of LCA allows the conjugates (CMD-SS-LCAs) to form self-assembled nanoparticles in aqueous conditions. Depending on the degree of LCA substitution, the particle diameters range from 163 to 242 nm. Doxorubicin (DOX), chosen as a model anticancer drug, is effectively encapsulated into the nanoparticles with high loading efficiency (>70%). In vitro optical imaging tests reveal that the fluorescence signal of DOX quenched in the bioreducible nanoparticles is highly recovered in the presence of glutathione (GSH), a tripeptide capable of reducing disulfide bonds in the intracellular compartments. Bioreducible nanoparticles rapidly release DOX when they are incubated with 10 mm GSH, whereas the drug release is greatly retarded in physiological buffer (pH 7.4). DOX-loaded bioreducible nanoparticles exhibit higher toxicity to SCC7 cancer cells than DOX-loaded nanoparticles without the disulfide bond. Confocal laser scanning microscopy observation demonstrate that bioreducible nanoparticles can effectively deliver DOX into the nuclei of SCC7 cells. In vivo biodistribution study indicates that Cy5.5-labeled CMD-SS-LCAs selectively accumulate at tumor sites after systemic administration into tumor-bearing mice. Notably, DOX-loaded bioreducible nanoparticles exhibit higher antitumor efficacy than reduction-insensitive control nanoparticles. Overall, it is evident that bioreducible CMD-SS-LCA nanoparticles are useful as a drug carrier for cancer therapy.

Antitumor activity of [Pt(O,O'-acac)(γ-acac)(DMS)] in mouse xenograft model of breast cancer

The higher and selective cytotoxicity of [Pt(O,O′-acac)(γ-acac)(DMS)] toward cancer cell in both immortalized cell lines and in breast cancer cells in primary cultures, stimulated a pre-clinical study so as to evaluate its therapeutic potential in vivo. The efficacy of [Pt(O,O′-acac)(γ-acac)(DMS)] was assessed using a xenograft model of breast cancer developed by injection of MCF-7 cells in the flank of BALB/c nude mice. Treatment of solid tumor-bearing mice with [Pt(O,O′-acac)(γ-acac)(DMS)] induced up to 50% reduction of tumor mass compared with an average 10% inhibition recorded in cisplatin-treated animals. Thus, chemotherapy with [Pt(O,O′-acac)(γ-acac)(DMS)] was much more effective than cisplatin. We also demonstrated enhanced in vivo pharmacokinetics, biodistribution and tolerability of [Pt(O,O′-acac)(γ-acac)(DMS)] when compared with cisplatin administered in Wistar rats. Pharmacokinetics studies with [Pt(O,O′-acac)(γ-acac)(DMS)] revealed prolonged Pt persistence in systemic blood circulation and decreased nefrotoxicity and hepatotoxicity, major target sites of cisplatin toxicity. Overall, [Pt(O,O′-acac)(γ-acac)(DMS)] turned out to be extremely promising in terms of greater in vivo anticancer activity, reduced nephrotoxicity and acute toxicity compared with cisplatin.

Antibody delivery of drugs and radionuclides: factors influencing clinical pharmacology

The therapeutic rationale of antibody conjugates is the selective delivery of a cytotoxin to tumor cells via binding and internalization of the monoclonal antibodies to a specific cell-surface antigen, thereby enhancing the therapeutic index of the cytotoxin. The key structural and functional components of an antibody conjugate are the antibody, the linker and the cytotoxin (chemical or radionuclide) with each component being critical for the successful development of the conjugate. Considerable efforts have been made in understanding the pharmacokinetics, pharmacodynamics, tissue distribution, metabolism and pharmacologic effects of these complex macromolecular entities. The purpose of this article is to discuss the properties and various structural components of antibody conjugates that influence their clinical pharmacology.

Cisplatin-loaded core cross-linked micelles: comparative pharmacokinetics, antitumor activity, and toxicity in mice

Polymer micelles with cross-linked ionic cores are shown here to improve the therapeutic performance of the platinum-containing anticancer compound cisplatin. Biodistribution, antitumor efficacy, and toxicity of cisplatin-loaded core cross-linked micelles of poly(ethylene glycol)-b-poly(methacrylic acid) were evaluated in a mouse ovarian cancer xenograft model. Cisplatin-loaded micelles demonstrated prolonged blood circulation, increased tumor accumulation, and reduced renal exposure. Improved antitumor response relative to free drug was seen in a mouse model. Toxicity studies with cisplatin-loaded micelles indicate a significantly improved safety profile and lack of renal abnormalities typical of free cisplatin treatment. Overall, the study supports the fundamental possibility of improving the potential of platinum therapy using polymer micelle-based drug delivery.

Antibody structure, instability, and formulation

The number of therapeutic monoclonal antibody in development has increased tremendously over the last several years and this trend continues. At present there are more than 23 approved antibodies on the US market and an estimated 200 or more are in development. Although antibodies share certain structural similarities, development of commercially viable antibody pharmaceuticals has not been straightforward because of their unique and somewhat unpredictable solution behavior. This article reviews the structure and function of antibodies and the mechanisms of physical and chemical instabilities. Various aspects of formulation development have been examined to identify the critical attributes for the stabilization of antibodies.

Tissue distribution evaluation of stealth pH-sensitive liposomal cisplatin versus free cisplatin in Ehrlich tumor-bearing mice

Multidrug resistance and drug toxicity represent major obstacles to cancer chemotherapy. Drug delivery systems, such as liposomes, offer improved chemical stability of encapsulated drugs, enhanced accumulation in tumors and decreased toxicity. The aim of this study was to evaluate the tissue distribution of stealth pH-sensitive liposomes containing cisplatin (SpHL-CDDP), compared with free cisplatin (CDDP), in solid Ehrlich tumor-bearing mice. After administering a 6 mg/kg single intravenous bolus injection of either free radiolabeled cisplatin or SpHL containing radiolabeled cisplatin, blood and tissues were analyzed for cisplatin content by determining radioactivity using an automatic scintillation apparatus. The area under the CDDP concentration-time curve (AUC) obtained for blood after SpHL-CDDP administration was 2.1 fold larger when compared with free CDDP treatment. The longer circulation of SpHL-CDDP led to a higher tumor AUC, and the determination of the ratio between AUC in each tissue and that in blood (Kp) showed a higher accumulation of CDDP in SpHL-CDDP administrated tumors. The SpHL-CDDP was also significantly uptaken by the liver and spleen. The distribution of SpHL-CDDP in these organs was extensive, revealing a high extravasation of CDDP to the tissues. The SpHL-CDDP kidney uptake was also greater than that of free CDDP; however, the Kp value found was lower. This indicates that the SpHL-CDDP led to a reduction of CDDP retention by renal tissue. Thus, these results indicate that the SpHL-CDDP may indeed be useful in alleviating renal damage induced by CDDP and thus represents a promising delivery system for cancer treatment through CDDP.

BR96-DOX immunoconjugate targeting of chemotherapy in brain tumor models

An immunoconjugate of doxorubicin (adriamycin) and a tumor-specific monoclonal antibody, BR96-DOX (now SGN-15) targets chemotherapy to cells that express the LewisY antigen. This immunoconjugate is internalized into lysosomes in antigen-expressing cells, with release of free doxorubicin after hydrolysis of the acid-labile linker. We review our studies using BR96-DOX in a human small-cell lung carcinoma intracerebral xenograft model in nude rats. We have found that the immunoconjugate is effective against intracerebral tumors when delivery is enhanced with osmotic disruption of the blood-brain barrier (BBB). Enhanced delivery of BR96-DOX with BBB opening can work together with radiotherapy to increase antitumor efficacy, which is maximally effective if immunoconjugate is administered prior to radiotherapy. In heterogeneous brain tumors, enhanced delivery of BR96-DOX significantly reduced tumor volumes, but local release of doxorubicin by targeting antigen expressing cells shows modest cytotoxicity against adjacent non-expressor cells. Although BR96-DOX is not effective against glioma cells tested, it does provide a model for drug-immunoconjugate therapy of gliomas. Our studies in a rat brain tumor model point out the importance of optimized delivery, antigenic heterogeneity, and bystander effect for brain tumor therapy. We review additional studies of drug-mAb immunoconjugates pertinent to the treatment of gliomas.

Effect of age on body distribution of Tityustoxin from Tityus serrulatus scorpion venom in rats

Previous research from our Laboratory has shown a greater susceptibility of young animals, when compared to adults, to envenomation by tityustoxin (TsTX), one of the main toxins from Tityus serrulatus scorpion venom. Our hypothesis is that a differential body distribution of TsTX among adult and young animals could account for the worse prognosis of scorpion envenomation in infants. Thus, TsTX labeled with technetium-99m was injected (6 microg, subcutaneous) in adult (150-160 day-old) and young (21-22 day-old) male rats. Groups of animals were sacrificed at different times after TsTX injection (0.08, 1.0, 3.0, 6.0, 12.0 and 24.0 hours) under Urethane anesthesia (140 mg/100 g, i.p.). The brain, heart, lungs, liver, kidneys, spleen and thyroid were excised and blood collected. Young rats presented a shorter latency toxin concentration peak in all studied organs except for the liver and the kidney, when compared to adults. The ratio between the area under the curve of the toxin concentration in each organ and that in blood (Kp) indicates higher accumulation in the organs of young animals mainly for brain, liver and heart. These observations suggest a faster toxin distribution in the organs of young rats. The higher uptake of TsTX in the brain is suggestive of a greater permeability for the toxin along the blood-brain barrier of young rats. In conclusion, the higher uptake in heart, together with data from the brain, may help to elucidate the clinical manifestations frequently observed in children under scorpion envenomation.

Cisplatin stops tubulin assembly into microtubules. A new insight into the mechanism of antitumor activity of platinum complexes

Despite numerous studies considering DNA as a primary target of cisplatin attack, this work is the first to show the pure effect of cisplatin on the process of tubulin assembly/disassembly in vitro. When platinated, tubulin does not assemble into microtubules (direct electron microscopic studies). In place of them, highly stable and inert circled rings arise. Such tubulin aggregates are unable to participate in the process of chromosome separation during the mitosis, thus blocking cell division in living cells, which is a direct evidence of cisplatin antitumor activity. Cisplatin attack on tubulin causing blockage of tubulin assembly occurs via a two-step binding to GTP in the GTP center of tubulin ((195)Pt, (31)P NMR studies). The calculated binding rates are close to those reported in cisplatin-DNA interactions. The mechanism of cisplatin attack on tubulin is proposed.

Altered tissue distribution and elimination of amikacin encapsulated in unilamellar, low-clearance liposomes (MiKasome)

PURPOSE

Amikacin in small unilamellar liposomes (MiKasome) has prolonged plasma residence (half-life > 24hr) and sustained efficacy in Gram-negative infection models. Since low-clearance liposomes may be subject to a lower rate of phagocytic uptake, we hypothesized this formulation may enhance amikacin distribution to tissues outside the mononuclear phagocyte system.

METHODS

Rats received one intravenous dose (50 mg/kg) of conventional or liposomal amikacin. Amikacin was measured for ten days in plasma, twelve tissues, urine and bile.

RESULTS

Liposomal amikacin increased and prolonged drug exposure in all tissues. Tissue half-lives (63-465 hr) exceeded the plasma half-life (24.5 hr). Peak levels occurred within 4 hours in some tissues, but were delayed 1-3 days in spleen, liver, lungs and duodenum, demonstrating the importance of characterizing the entire tissue concentration vs. time profile for liposomal drugs. Predicted steady-state tissue concentrations for twice weekly dosing were >100 microg/g. Less than half the liposomal amikacin was recovered in tissues and excreta, suggesting metabolism occurred. Amikacin was not detected in plasma ultrafiltrates. Tissue-plasma partition coefficients (0.2-0.8 in most tissues) estimated from tissue-plasma ratios at Tmax were similar to those estimated from tissue AUCs.

CONCLUSIONS

Low-clearance liposomal amikacin increased and prolonged drug residence in all tissues compared to conventional amikacin. The long tissue half-lives suggest liposomal amikacin is sequestered within tissues, and that an extended dosing interval is appropriate for chronic or prophylactic therapy with this formulation.