Camptothecin Derivatives Research Articles

New camptothecin derivatives for generalized oncological chemotherapy: Synthesis, stereochemistry and biology

Derivatives of SN38 were synthesized that were either monosubstituted at C-5 or C-9 or disubstituted at both C-5 and C-9. Substitution to C-5 led to the generation of pairs of diastereomers (2c-2 h) in a one-pot reaction and was readily separable by HPLC. The absolute configurations of C-5 were established by electronic circular dichroism experiments. Compounds were tested in vitro against human cancer cell lines as well as a normal cell line. The impact of compounds 2a–2j on cancer cells is significant and the IC50 values against the normal cell line are several times higher than that of SN38. Using the Mannich reaction we obtained a new innovative group of derivatives with unique biological properties that preserves the high cytotoxicity in cancer cells and eliminates the acute toxicity to non-neoplastic cells, which can be considered a breakthrough in chemotherapy with the use of topoisomerase I inhibitors from the camptothecin family.

CD147 Monoclonal Antibody Targeted Reduction-Responsive Camptothecin Polyphosphoester Nanomedicine for Drug Delivery in Hepatocellular Carcinoma Cells.

In the treatment of tumor-targeted small-molecule anti-cancer drugs, antibody-mediated therapies, especially for antibody-drug conjugates (ADCs), have revealed great latent force. However, the therapeutic drugs provided by ADCs possess limitation. Considering that the combination of antibodies and nano-drugs can broaden their applicability in the field of tumor treatment, herein, we developed an antibody conjugated polymeric prodrug nanoparticles SAE-PEG-b-PBYP-ss-CPT for targeted camptothecin (CPT) delivery to liver tumor cells. The diblock copolymer was composed of PEG and biodegradable polyphosphoester (PBYP) containing alkynyl groups in the side chain. A derivative of CPT (CPT-ss-N3) was bonded to the PBYP via "click" reaction. The diethyl squarate (SAE) in the terminal of PEG chain was used as a functional group to bond with CD147 monoclonal antibody (CD147 mAb). The particle size and size distribution of the both nanoparticles, with antibody binding (namely CD147-CPT NPs) and without antibody (abbreviated as CPT-loaded NPs), were measured by dynamic light scattering (DLS). The morphologies of both two kinds of nanoparticles were observed by transmission electron microscope (TEM). The results of X-ray photoelectron spectroscopy (XPS) showed that CD147 mAb had been coupled to the surface of CPT-loaded NPs. Endocytosis test indicated that CD147-CPT NPs had higher uptake rate and accumulation in HepG2 cells than those of CPT-loaded NPs without antibodies, due to CD147 mAb can specifically bind to CD147 protein overexpressed in HepG2 cells. We establish a method to bond monoclonal antibodies to anti-cancer polymeric prodrugs, and endow biodegradable polymeric prodrugs with precise targeting functions to liver cancer cells.

In-silico Studies and Wet-Lab Validation of Camptothecin Derivatives for Anti-Cancer Activity Against Liver (HepG2) and Lung (A549) Cancer Cell Lines.

In the present study, we have explored the utility of QSAR modelling, in silico ADMET, docking, chemical semi-synthesis, and in vitro evaluation studies for the identification of active camptothecin (CPT) derivatives against cancer-targeting human liver (HepG2) and lung (A549) cancer cell lines. Two QSAR models were developed as screenings tools using the multiple linear regression (MLR) method followed by ADMET and docking studies. The regression coefficient (r2) and cross-validation regression coefficients (rCV2T) of the QSAR model for the HepG2 cell line was 0.95 and 0.90, respectively, and for the A549 cell line, it was 0.93 and 0.81, respectively. In silico studies show that CPT derivatives (CPT-1 and CPT-6) possess drug-like properties. Docking performed on DNA Topoisomerase-I showed significant binding affinity. Finally, predicted active derivatives were chemically semi synthesized, spectroscopically characterized, and evaluated in-vitro for cytotoxic/anticancer activity against HepG2 and A549 cell lines. The experimental results are consistent with the predicted results. These findings may be of immense importance in the anticancer drug development from an inexpensive and widely available natural product, camptothecin.

Endophytic fungus Diaporthe caatingaensis MT192326 from Buchanania axillaris: An indicator to produce biocontrol agents in plant protection

The study aims at the Isolation, screening and antibacterial evaluation of Camptothecin (CPT) and its derivatives, an anticancer molecule from endophytic fungus Diaporthe caatingaensis MT192326 of the medicinal plant, Buchanania axillaris. Plant parts were collected from Sathyamangalam Tiger Reserve forest, Tamil Nadu. The fungus was isolated using DEKM07 medium was used as the screening medium for the presence of CPT. The strain with the highest yield of CPT was identified at the molecular level by 18S rDNA sequencing. CPT was isolated and analyzed by UV–Vis spectrophotometry, Thin layer chromatography, High-Performance Liquid Chromatography, Fourier Transform Infrared spectroscopy, and Electron spray ionization-mass spectrometry. The compounds identified by ESI-MS from the fungal extract were studied for their antibacterial assays against procured MTCC bacterial pathogens. The maximum yield of 0.681 mg/L of CPT was produced by the fungus D.caatingaensis. CPT derivatives were identified at m/z of 305, 348 and 389 through ESI-MS analysis. Antibacterial studies revealed that the endophytic fungal extract compounds were studied for antibacterial activities of disc diffusion assay, exhibiting a growth inhibition range of 15–22 mm in nutrient agar plate medium. The Minimum Inhibitory Concentration revealed the antibacterial potential at a lower concentration of 12.5–25 μg/ml with all bacteria studied. The relatively lower antimicrobial efficacy of partially purified bio-metabolites than the positive control streptomycin (3.125) concentration could be due to the presence of derivatives of the compounds that hinder the activity of the biometabolite. This is the first initiative to screen, isolate and analyze the antibacterial assays of CPT and derivatives from endophytic fungus D.caatingaensis of ethnopharmacologically important B.axillaris plant from STRF.

Orchids as Potential Sources of Anticancer Agents: Our Experience

Cancer is the second leading cause of death globally and the cancer burden continues to grow, exerting tremendous physical, emotional and financial strain on individuals, families, communities and health systems. Many health systems in low- and middle-income countries are ill-prepared to manage this burden, and around the world large numbers of cancer patients do not have access to timely quality diagnosis or treatment. Natural products, especially originated from plants, have been applied as remedies to treat various diseases, including cancer, for thousands of years. Several anticancer agents derived from plants, such as paclitaxel (taxol), vinblastine, vincristine, camptothecin derivatives, podophyllotoxins, are in clinical use and a number of other promising agents are in preclinical or clinical development. A growing number of bioactive compounds with cytostatic and cytotoxic activities to treat cancer have been isolated from several orchid species. The Annapurna Research Center in collaboration with other academic institutions is engaged in identifying and exploring anticancer compounds in orchids of Nepal. The center has identified ten different orchid species which contain high phenol and flavonoid contents evidently showing anticancer activities in our in vitro assays against different cancer cell lines viz cervical cancer, lung cancer and brain tumor cell lines. These findings demonstrate that orchids which have been used in in various formulations in traditional medicine since ancient times qualify as potential source for novel drug candidates or starting points for further lead optimization towards clinical candidates for the most urgently needed treatment of aggressive types of cancer. This review paper highlights that in all likelihood; our contributions in orchid research here in Nepal could bring great relief to patients with cancer globally.

Self-assembled Camptothecin derivatives – Curcuminoids conjugate for combinatorial chemo-photodynamic therapy to enhance anti-tumor efficacy

Camptothecin (CPT), an alkaloid, was first discovered from plants and has potent anti-tumor activity. Since then, CPT analogs (namely Irinotecan and Topotecan) have been approved by the FDA for cancer treatments. Curcumin, on the other hand, is a widely used photosensitizer in photodynamic therapy (PDT) treatment. In our previous work, we have reported a straightforward strategy to construct a drug self-delivery system in which two-molecular species Irinotecan and Curcumin can self-assembly into a complex of ion pairs, namely ICN, through intermolecular non-covalent interactions. We found that ICN has slightly better chemotherapy efficacy than its individual components with much fewer side effects. In this paper, we aim to combine the chemotherapy and the PDT of ICN to further improve its anti-tumor performance. The efficient cellular uptake of ICNs was observed by confocal microscopy. Dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay was used to detect the generation of singlet oxygen species. We found that the cell viability was 9% with both chemotherapy and PDT, and 31% with chemotherapy alone for the case with an ICN concentration of 10 μM, which demonstrated that the anti-tumor efficacy against the HT-29 cancer cell line was enhanced substantially with the combination therapy strategy. The study with an in vivo mouse model has further verified that the chemo-PDT dual therapy can inhibit tumor growth by 84% and 18.8% comparing with the control group and the chemotherapy group, respectively. Our results demonstrated that the new strategy using self-assembly and carrier-free nanoparticles with their chemo-PDT dual therapy may provide new opportunities to develop future combinatorial therapy methods in treating cancer.

A NMR study of binding the metabolite of SN38 derivatives to a model nicked DNA decamer mimicking target of Topo I inhibitors

In this account we present NMR based results of the interaction of 7-ethyl-9-hydroxymethyl-10-hydroxycamptothecin (1), a derivative of SN38, with a model nicked DNA decamer mimicking the wild type DNA target of Topoisomerase I inhibitors from the camptothecin family. The title compound 1 can be considered a main metabolite of phase I in the metabolic pathway of camptothecin derivatives bearing the alkylamino substituent. Therefore, its pharmacodynamic properties are of interest. It was established by DOSY (Diffusion Ordered Spectroscopy) that compound 1 forms a fairly stable molecular complex with a model nicked DNA decamer with affinity constant Ka 3.02 mM−1. The analysis of NOESY experiments revealed intermolecular cross peaks and mutual induced shifts on both interacting components allowing the conclusion that guest molecule 1 is stacking the nitrogen bases inside the nick. MD (Molecular Dynamics) analysis of four possible inclusions of 1 inside the nick allows establishing the detailed geometry of a complex. Two conformations are suggested as the ones best representing the results of molecular modeling reconciled with experimental NOESY results. The aromatic core of both structures is stacking the nitrogen bases in a nick facing the unbroken strand with ring A. The protons in ring E interact with ribose protons of edge bases of a nick. In conclusion, it can be asserted that SN38 derivative 1 can effectively bind the molecular target of Topo I enzyme and play a role as a Topo I inhibitor.

Camptothecin: An anticancer drug from Pestalotiopsis microspora Mh458929 – An endophytic fungus isolated from an ethnopharmacologically important medicinal plant Cordia dichotoma G. forst

Background: Endophytic fungi that live asymptomatically inside the plant tissues have novel bioactive metabolites exhibiting a variety of biological activities, especially against cancer. Cordia dichotoma G. Forst. play a significant role in traditional medicines and therapeutics. Leaves and bark have been used as anti-inflammatory and anticancer agents. Objectives: Isolation, screening, and in silico toxicity evaluation of camptothecin (CPT) from the endophytic fungus Pestalotiopsis microspora MH458929. Materials and Methods: Endophytic fungus was isolated from leaves of C. dichotoma collected from Sathyamangalam Tiger Reserve forest (STRF), Tamil Nadu. The wild strain was identified by 18S rDNA sequencing. Modified potato dextrose broth was used as a screening medium for the presence of CPT. CPT was analyzed by high-performance liquid chromatography and electrospray ionization–mass spectrometry (ESI-MS). Compounds identified by ESI-MS from fungal extract were further studied for their in silico toxicity study against Daphnia magna, Tetrahymena pyriformis, Pimephales promelas, and Rattus sp. Bioaccumulation factors, developmental toxicity, and mutagenicity were studied by the quantitative structure–activity relationship model – Toxicity Estimation Software Tool. Results: Endophytic fungus P. microspora produced a maximum yield of 0.691 mg/L of CPT. CPT derivatives were identified at m/z of 349.10, 363.08, and 389.41 through ESI-MS analysis. In silico toxicity study revealed that compounds were of Category D and hence considered nontoxic to higher organisms. However, compounds showed high toxicity for lower organisms, with toxicity order D. magna > T. pyriformis > P. promelas > rat. Conclusion: The present study is the first report to screen, isolate, and analyze the CPT's in silico toxicity and its derivatives from endophytic fungus P. microspora from STRF. Further in vitro and in vivo studies are recommended to utilize CPT and its derivatives in pharmaceuticals.

Synthesis and Biological Evaluation of 10-Substituted Camptothecin Derivatives with Improved Water Solubility and Activity.

Despite remarkable clinical achievements, camptothecin (CPT) still suffers from poor solubility and severe toxicity. Therefore, it is necessary to redevelop CPT derivatives as supplementary antitumor agents with good water solubility and small side effects. In this work, 27 camptothecin derivatives were synthesized and screened for their cytotoxicity against A549 (lung) and HCT-116 (colon) cancer cell lines. Among them, compound B7, 7-ethyl-10-(2-oxo-2-(4-methylpiperidin-1-yl)ethoxy)camptothecin,was demonstrated in vitro to be a more potent antitumor agent than SN-38 by comparison of their inhibitory activities against cell proliferation and colony formation and interference effect on process of cell cycle and cell apoptosis. Additionally, a molecular docking model revealed that B7 can interact with the topoisomerase I-DNA complex, and that the solubility of B7 reached 5.73 μg/mL in water. Moreover, B7 significantly inhibited tumor growth in an A549 xenograft model at dosages of 0.4 and 2.0 mg/kg, and exhibited minimum lethal doses comparable to those of irinotecan. These results indicated that B7, with improved solubility, enhanced activity and acceptable acute toxicity, can be used as a lead compound for the development of novel anticancer agents.

Bifunctional Aptamer Drug Carrier Enabling Selective and Efficient Incorporation of an Approved Anticancer Drug Irinotecan to Fibrin Gels

We have previously developed a bifunctional aptamer (bApt) binding to both human thrombin and camptothecin derivative (CPT1), and showed that bApt acts as a drug carrier under the phenomenon named selective oligonucleotide entrapment in fibrin polymers (SOEF), which enables efficient enrichment of CPT1 into fibrin gels, resulting in significant inhibition of tumor cell growth. However, although the derivative CPT1 exhibits anticancer activity, it is not an approved drug. In this study, we evaluated the binding properties of bApt to irinotecan, a camptothecin analog commonly used for anticancer drug therapy, in addition to unmodified camptothecin (CPT). Furthermore, we have revealed that irinotecan binds to bApt like CPT1 and is selectively concentrated on fibrin gels formed around the tumor cells under the SOEF phenomenon to suppress cell proliferation.

SGN-CD30C, an Investigational CD30-Directed Camptothecin Antibody-Drug Conjugate (ADC), Shows Strong Anti Tumor Activity and Superior Tolerability in Preclinical Studies

SGN-CD30C, an investigational CD30-directed ADC, utilizes a potent novel camptothecin derivative as the cytotoxic payload. SGN-CD30C targets the same antigen as brentuximab vedotin (BV), though the payload has a different mechanism of action, namely inhibiting topoisomerase I rather than disrupting microtubules. Unlike monomethyl auristatin E, camptothecin-based therapies do not cause peripheral neuropathy clinically, suggesting that SGN-CD30C may have the potential to avoid one of the most common adverse events associated with BV. In preclinical studies, SGN-CD30C demonstrated strong monotherapy activity, inducing durable tumor regressions in multiple lymphoma models and eliciting cures in a BV-resistance tumor model (Figure 1). Moreover, SGN-CD30C exhibits many of the desirable attributes associated with BV, notably, bystander activity and CD30+ T regulatory cell (Treg) depletion. Using an admixed model of CD30+ and CD30-tumor cells, SGN-CD30C demonstrated robust anti-tumor activity in vivo, confirming SGN-CD30C can induce bystander killing of antigen-negative tumor cells in CD30-heterogeneous tumors. Additionally, SGN-CD30C depleted CD30+ Treg cells in vitro (Figure 2), suggesting it has the potential to exert activity through multiple mechanisms of action. SGN-CD30C was well-tolerated in non-human primate toxicology studies and demonstrated ~6-fold higher maximum tolerated dose when compared to BV. The primary toxicity for SGN-CD30C in non-human primates (NHP) studies was anemia due primarily to bone marrow suppression of erythropoiesis. SGN-CD30C had no effect on neutrophil counts and caused only minimal to mild decreases in platelets. The lack of significant neutropenia seen with SGN-CD30C contrasts with BV, indicating the two ADCs may have non-overlapping dose limiting toxicities. Hematology parameters show SGN-CD30C is tolerated at a 10-fold higher dose than BV with weekly dosing, suggesting SGN-CD30C may offer the potential for increased dose density. In summary, our data show SGN-CD30C is a compelling therapeutic candidate for CD30-positive malignancies. The distinct mechanism of action, strong anti-tumor activity, and enhanced tolerability provide a strong rationale to clinically investigate SGN-CD30C across the CD30-expressing lymphoma landscape. A Phase 1 clinical trial is planned to investigate SGN-CD30C in relapsed and refractory lymphoma. Disclosures Heiser: Seattle Genetics: Current Employment, Current equity holder in publicly-traded company. Grogan:Seattle Genetics: Current Employment, Current equity holder in publicly-traded company. Jin:Seattle Genetics: Current Employment, Current equity holder in publicly-traded company. Conerly:Seattle Genetics: Current Employment, Current equity holder in publicly-traded company.

Synthesis and biological evaluation of camptothecin substituted norcantharimide derivatives

In this paper, a series of novel derivatives of camptothecin substituted norcantharimide was designed by mimic strategy. These compounds were synthesized in moderate yields by directly coupling CPT with N-amino acid norcantharimides. Their cytotoxicity to four human tumour cell lines (HepG2, BGC-803, SW480 and PANC-1) and normal human cell lines L-O2 and HIEC was evaluated. The synthesized CPT substituted norcantharimide analogs (3g and 3f) showed better anti-hepatocarcinoma activity than CPT. Compounds 3d, 3e, 3g, 3h and 3i also showed strong inhibition activity against BGC803.

Natural Products as Anti-Cancerous Therapeutic Molecules Targeted towards Topoisomerases.

Topoisomerases are reported to resolve the topological problems of DNA during several cellular processes, such as DNA replication, transcription, recombination, and chromatin remodeling. Two types of topoisomerases (Topo I and II) accomplish their designated tasks by introducing single- or double-strand breaks within the duplex DNA molecules, and thus maintain the proper structural conditions of DNA to release the topological torsions, which is generated by unwinding of DNA to access coded information, in the course of replication, transcription, and other processes. Both the topoisomerases have been looked at as crucial targets against various types of cancers such as lung, melanoma, breast, and prostate cancers. Conceptually, targeting topoisomerases will disrupt both DNA replication and transcription, thereby leading to inhibition of cell division and consequently stopping the growth of actively dividing cancerous cells. Since the discovery of camptothecin (an alkaloid) as an inhibitor of Topo I in 1958, a number of derivatives of camptothecin were developed as potent inhibitors of Topo I. Two such derivatives of camptothecin, namely, topotecan and irinotecan, have been commonly used as US Food and Drug Administration (FDA) approved drugs against Topo I. Similarly, the first Topo II inhibitor, namely, etoposide, an analogue of podophyllotoxin, was developed in 1966 and got FDA approval as an anti-cancer drug in 1983. Subsequently, several other inhibitors of Topo II, such as doxorubicin, mitoxantrone, and teniposide, were developed. These drugs have been reported to cause accumulation of cytotoxic non-reversible DNA double-strand breaks (cleavable complex). Thus, the present review describes the anticancer potential of plant-derived secondary metabolites belonging to alkaloids, flavonoids and terpenoids directed against topoisomerases. Furthermore, in view of the recent advances made in the field of computer-aided drug design, the present review also discusses the use of computational approaches such as ADMET, molecular docking, molecular dynamics simulation and QSAR to assess and predict the safety, efficacy, potency and identification of these potent anti-cancerous therapeutic molecules.

Pathway-dependent supramolecular polymerization of camptothecin derivatives into filaments for chemotherapy and imaging

Constructing supramolecular structures via non-covalent interactions depends on the assembly pathway selection, which has attracted much interest in chemistry, materials science, and nanomedicine. Despite recent advances in the formation of a variety of splendid nanostructures in amphiphile assembly, the relationship between the conformation of formed nanostructures and their function (chemotherapy) is less explored, especially in biological systems (i.e., cell and animal). Here we report that nanostructures formed through different assembly pathways of small molecules (i.e., camptothecin derivative) result in distinct cellular distribution and activities toward colon cancer in the cell-based assay and tumor-bearing mouse model. Specifically, conjugation of laminin derivative peptide and hydroxycamptothecin (HCPT) results in nanoparticles with confined conformation, which suppresses the activity of HCPT. The enzyme-instructed polymerization of HCPT-1 results in uniform filaments with an α-helical-like structure, which restores the conformation of laminin derivative peptide and the activity of HCPT both in vitro and in vivo. Replacing HCPT with other functional small molecules also exhibit similar results in our system. This study facilitates the development of functional assemblies with confined conformation for chemotherapy and imaging.

Abstract 2889: SGN-CD30C, a new CD30-directed camptothecin antibody-drug conjugate (ADC), shows strong anti-tumor activity and superior tolerability in preclinical studies

Abstract SGN-CD30C, a new CD30-directed ADC, utilizes a potent camptothecin derivative as the cytotoxic payload. SGN-CD30C targets the same antigen as brentuximab vedotin (BV), though the payload has a different mechanism of action, namely inhibiting topoisomerase I rather than disrupting microtubules. Unlike monomethyl auristatin E, camptothecin-based therapies do not cause peripheral neuropathy clinically, suggesting that SGN-CD30C may have the potential to avoid one of the most common adverse events associated with BV. In preclinical studies, SGN-CD30C demonstrated strong monotherapy activity, inducing durable tumor regressions in multiple lymphoma models and eliciting cures in a BV-resistant tumor model. Furthermore, bystander killing of antigen-negative tumor cells, which is thought to be an important attribute of BV, was confirmed in vivo using CD30-heterogeneous tumors. SGN-CD30C was well-tolerated in non-human primate (NHP) toxicology studies and demonstrated ~6-fold higher maximum tolerated dose (MTD) when compared to BV. The primary toxicity for SGN-CD30C in NHP studies was anemia due primarily to bone marrow suppression of erythropoiesis. SGN-CD30C had no effect on neutrophil counts and caused only minimal to mild decreases in platelets. The lack of significant neutropenia seen with SGN-CD30C contrasts with BV, indicating the two antibody-drug conjugates may have non-overlapping dose limiting toxicities. We theorized using a reduced dose of BV in combination with SGN-CD30C could provide a dual mechanism of action to retain or enhance anti-tumor activity while decreasing the incidence of non-overlapping toxicities (i.e. peripheral neuropathy). To test this hypothesis preclinically, we evaluated the anti-tumor activity of BV and SGN-CD30C at sub-curative doses in a Karpas-299 xenograft model. The results show the combination of SGN-CD30C + BV generated a higher number of durable CRs compared to the equivalent monotherapy doses, thereby confirming strong anti-tumor activity by using a lower dose of each ADC in combination. In summary, our data show SGN-CD30C is a compelling therapeutic candidate for CD30-positive malignancies. The strong anti-tumor activity and superior tolerability suggest SGN-CD30C has a favorable therapeutic window. Furthermore, the distinct mechanism of action and non-overlapping toxicity profile offers the potential to combine SGN-CD30C with BV for enhanced risk/benefit. Citation Format: Maureen Ryan, Ryan Lyski, Lauren Bou, David Meyer, Steven Jin, Jessica Simmons, Dennis Benjamin, Peter Senter, Scott Jeffrey. SGN-CD30C, a new CD30-directed camptothecin antibody-drug conjugate (ADC), shows strong anti-tumor activity and superior tolerability in preclinical studies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2889.

Engineered liposomes bearing camptothecin analogue for tumour targeting: in vitro and ex-vivo studies

Topotecan (TPT) is a semi-synthetic, water-soluble derivative of camptothecin, which inhibits the action of topoisomerase I in the S-phase of the cell cycle leading to cell death. For the effective delivery of TPT to cancer cells, pH-sensitive sialic acid modified liposomes were developed. These liposomes were prepared by the thin-film hydration method using the active loading technique. Vesicle size, polydispersity index (PDI), zeta potential, and percentage entrapment efficiency were determined to be 167 ± 3.78 nm, 0.243, −8.39 mV, and 79.88 ± 1.67%, respectively. The pH-sensitive sialic acid (SA) conjugated liposomes enhanced the drug release at acidic pH 4 (92.33 ± 4.21%) as compared to physiological pH 7.4 (63.11 ± 4.51%). A Sulforhodamine B (SRB) cytotoxicity assay was performed in Murine sarcoma S180 cell lines and the GI50 value of free TPT, Lipo, P-Lipo, SA-P-Lipo, and Adriamycin (ADR) were determined to be 10.07 ± 0.15, 27.33 ± 1.01, 28.76 ± 0.87, 15.7 ± 0.45, and 11.5 ± 0.21 µg/mL, respectively. Results obtained from the apoptosis study revealed that cell death by a combination of early apoptosis and apoptosis caused by SA-P-Lipo was ∼24 fold higher than the control. These results demonstrated that pH-sensitive sialic acid conjugated liposomes will be a potential formulation for improving the antitumor efficacy of TPT. However, further research is necessitated to expedite its applicability in clinical regimen in order to ascertain its safety and efficacy.

The Indenoisoquinoline LMP517: A Novel Antitumor Agent Targeting both TOP1 and TOP2.

The camptothecin derivatives topoisomerase I (TOP1) inhibitors, irinotecan and topotecan, are FDA approved for the treatment of colorectal, ovarian, lung and breast cancers. Because of the chemical instability of camptothecins, short plasma half-life, drug efflux by the multidrug-resistance ABC transporters, and the severe diarrhea produced by irinotecan, indenoisoquinoline TOP1 inhibitors (LMP400, LMP776, and LMP744), which overcome these limitations, have been developed and are in clinical development. Further modifications of the indenoisoquinolines led to the fluoroindenoisoquinolines, one of which, LMP517, is the focus of this study. LMP517 showed better antitumor activity than its parent compound LMP744 against H82 (small cell lung cancer) xenografts. Genetic analyses in DT40 cells showed a dual TOP1 and TOP2 signature with selectivity of LMP517 for DNA repair-deficient tyrosyl DNA phosphodiesterase 2 (TDP2)- and Ku70-knockout cells. RADAR assays revealed that LMP517, and to a lesser extent LMP744, induce TOP2 cleavage complexes (TOP2cc) in addition to TOP1ccs. Histone γH2AX detection showed that, unlike classical TOP1 inhibitors, LMP517 targets cells independently of their position in the cell cycle. Our study establishes LMP517 as a dual TOP1 and TOP2 inhibitor with therapeutic potential.

F10, a new camptothecin derivative, was identified as a new orally–bioavailable, potent antitumor agent

Topoisomerases are interesting targets for drug discovery. In the present study, we attached saturated carbon atoms to the 10-position of camptothecin and synthesized 10 new camptothecin derivatives from 10-HCPT or SN-38. The activities of new compounds were evaluated both in vitro and in vivo. The most promising compound F10, 7-ethyl-10-(2-oxo-2-(piperidin-1-yl)ethoxy)camptothecin, inhibited cancer cells growth with the IC50 of 0.002, 0.003, 0.011 and 0.081 μM on Raji, HCT116, A549 and Lovo cells, respectively. Meanwhile, oral administration of F10 remarkably suppressed the HCT116-xenograft tumor growth in the nude-mice model at the dosage of 0.5, 2.0 and 8.0 mg/kg in vivo. Intraperitoneal administration of F10 can completely inhibit Raji-xenograft tumor growth in established NPG mouse model at 2.0 and 4.0 mg/kg. In addition, the minimum lethal doses of F10 and SN-38 in mice by intravenous administration were 80 and 40 mg/kg (or 0.155, 0.102 mmol/kg), respectively. The solubility of F10 reached 9.86 μg/mL in a buffer solution of pH 4.5. The oral bioavailability of F10 achieved 22.4% in mice. The molecular docking model revealed that F10 can interact with topoisomerase I-DNA complex. Our findings indicate that F10 is a new orally-oavailable antitumor agent with potent anticancer effect. Furthermore, attaching a ring hydrophobic moiety to the 10-position of camptothecin provides a favorable approach in the optimization of camptothecin.

The novel camptothecin derivative, CPT211, induces cell cycle arrest and apoptosis in models of human breast cancer

ObjectiveBreast cancer is the second leading cause of cancer deaths in women worldwide and represents a highly aggressive nature with limited therapeutic options; thus, investigating novel therapeutic agents for breast cancer is much needed. In this study, we investigated the anticancer effects of a novel camptothecin derivative, CPT211, against human breast cancer. MethodsWe used hormone receptor-positive MCF-7, triple-negative (TNBC) MDA-MB-231, and HER2-positive BT-474 human breast cancer cells to examine cytotoxicity of CPT211. We measured cell viability with dose dependence of CPT211 treatments by an MTT assay and investigated the potential underlying mechanism through flow cytometric and Western blot methods. Furthermore, we evaluated the efficacy of the treatment combination of CPT211 and doxorubicin in a mouse model bearing MDA-MB-231 xenografts. ResultsCPT211 treatment led to dose-dependent decreases in cell viability of both MCF-7 and MDA-MB-231 cells, but not BT-474 cells. Analysis of the underlying molecular mechanism revealed that CPT211 activated p53-mediated apoptosis, by triggering intrinsic and extrinsic apoptotic pathways in MCF-7 cells. Additionally, CPT211 induced apoptosis and cell cycle arrest of MDA-MB-231 cells by activating Fas/FADD/caspase-8 signaling, suggesting that CPT211-mediated MDA-MB-231 cell apoptosis may occur through an extrinsic apoptosis pathway. CPT211 treatment with doxorubicin in mice bearing MDA-MB-231 xenografts was shown to enhance caspase-8 and caspase-7 activation, resulting in significant inhibition of tumor growth. ConclusionsThese results indicate that Fas/FADD/caspase-8 activation plays an important role in CPT211-mediated tumor growth suppression in TNBC, and the novel camptothecin derivative, CPT211, can be exploited for specific targeted therapies and potentially improve approaches to combination treatments for human breast cancer.

A phase Ib study of simmitecan (LP) single-agent and in combination with 5-fluorouracil/leucovorin (5-FU/LV) or thalidomide (T) in patients with advanced solid tumor.

3523 Background: Simmitecan (LP), a novel 9-substituted lipophilic camptothecin derivative, is a potent inhibitor of topoisomerase I with anti-tumor activity single agent or in combination with other anti-tumor agents, i.e. thalidomide or anti-PD-1 antibody in xenograft models. In this phase Ib study (NCT02870036), we evaluate the safety and anti-tumor effects of LP as monotherapy or in combination therapies in patients (pts) with advanced solid tumors. Methods: This open-label, multi-cohort phase Ib study was conducted at 3 academic centers in China. Eligible pts had advanced cancer without standard treatment options. Prior irinotecan treated failure pts was eligible. In the single agent study, enrolled pts was allocated to received intravenous(iv) 50, 80, or 120 mg/m2 of LP Q2W to determine the safety of LP. After single agent study finished, enrolled pts allocated in LP+5-FU/LV cohorts received 50, 65, or 80 mg/m2 of LP then LV 400 mg/m2 and 5-FU bolus at 400 mg/m2 followed by 5-FU continuous iv of 2400 mg/m2 Q2W; pts in LP+T cohorts received LP 65 mg/m2 Q2W + thalidomide 50mg QD or thalidomide 100mg QD, or LP 80 mg/m2 Q2W + thalidomide 50mg QD. Treatment repeated in 28-day cycles until disease progression or unacceptable toxicity. Results: Between October 2016 to February 2019, 41 pts, median age of 55.1 (range 29-69) years, were enrolled, 13 in LP monotherapy, 10 in LP + 5-FU/LV and 18 in LP + T. Over all, no dose limited toxicity (DLT) occurred. The most common (≥20%) grade 3/4 AE among three regimens was neutropenia (44%, 70% and 89% respectively in LP, LP+5FU/LV and LP+T),and treatment related SAEs were similar, i.e. anemia and febrile neutropenia (11.1% each) in LP, diarrhea (10%) in LP+5-FU/LV, febrile neutropenia (5.6%) in LP+T. Majority of enrolled pts (24/41, 59%) had progressed on prior irinotecan, nevertheless, partial response (PR) was observed in 1 colorectal cancer pt treated with LP 80 mg/m2 + thalidomide 50mg. Disease control rate (DCR, SD≥12 weeks or CR or PR) were 60%, 80% and 61% and median progress free survival were 2.71, 4.17 and 2.76 months respectively in LP, LP + 5-FU/LV and LP+T cohorts. Conclusions: This study showed the safety profiles are manageable, either LP monotherapy or combination therapies, no DLT or safety concern was elicited in combination compared to single agent, and the LP + 5-FU/LV regimen showed higher DCR. A phase II study in pts with metastatic NEC is on-going to explore safety and efficacy of LP + 5-FU/LV regimen combined with toripalimab, an anti-PD-1 antibody. Clinical trial information: 02870036 .