Preclinical Evaluation of 111In-Labeled PEGylated Maytansine Nimotuzumab Drug Conjugates in EGFR-Positive Cancer Models

Targeting EGFR with molecular degraders as a promising strategy to overcome resistance to EGFR inhibitors

Abnormal activation of EGFR is often associated with various malignant tumors, making it an important target for antitumor therapy. However, traditional targeted inhibitors have several limitations, such as drug resistance and side effects. Many studies have focused on the development of EGFR degraders to overcome this resistance and enhance the therapeutic effect on tumors. Proteolysis targeting chimeras (PROTAC) and Lysosome-based degradation techniques have made significant progress in degrading EGFR. This review provides a summary of the structural and function of EGFR, the resistance, particularly the research progress and activity of EGFR degraders via the proteasome and lysosome. Furthermore, this review aims to provide insights for the development of the novel EGFR degraders.

Effectiveness of [67Cu]Cu-trastuzumab as a theranostic against HER2-positive breast cancer

PURPOSE

To evaluate the imaging and therapeutic properties (theranostic) of 67Cu-labeled anti-human epidermal growth factor receptor II (HER2) monoclonal antibody trastuzumab against HER2-positive breast cancer (BC).

METHODS

We conjugated trastuzumab with p-SCN-Bn-NOTA, 3p-C-NETA-NCS, or p-SCN-Bn-DOTA, and radiolabeled with [67Cu]CuCl2. Immunoconjugate internalization was evaluated in BT-474, JIMT-1 and MCF-7 BC cells. In vitro stability was studied in human serum (HS) and Phosphate Buffered Saline (PBS). Flow cytometry, radioligand binding and immunoreactive fraction assays were carried out. ImmunoSPECT imaging of [67Cu]Cu-NOTA-trastuzumab was done in mice bearing BT-474, JIMT-1 and MCF-7 xenografts. Pharmacokinetic was studied in healthy Balb/c mice while dosimetry was done in both healthy Balb/c and in athymic nude mice bearing JIMT-1 xenograft. The therapeutic effectiveness of [67Cu]Cu-NOTA-trastuzumab was evaluated in mice bearing BT-474 and JIMT-1 xenografts after a single intravenous (i.v.) injection of ~ 16.8 MBq.

RESULTS

Pure immunoconjugates and radioimmunoconjugates (> 95%) were obtained. Internalization was HER2 density-dependent with highest internalization observed with NOTA-trastuzumab. After 5 days, in vitro stabilities were 97 ± 1.7%, 31 ± 6.2%, and 28 ± 4% in HS, and 79 ± 3.5%, 94 ± 1.2%, and 86 ± 2.3% in PBS for [67Cu]Cu-NOTA-trastuzumab, [67Cu]Cu-3p-C-NETA-trastuzumab and [67Cu]Cu-DOTA-trastuzumab, respectively. [67Cu]Cu-NOTA-trastuzumab was chosen for further evaluation. BT-474 flow cytometry showed low KD, 8.2 ± 0.2 nM for trastuzumab vs 26.5 ± 1.6 nM for NOTA-trastuzumab. There were 2.9 NOTA molecules per trastuzumab molecule. Radioligand binding assay showed a low KD of 2.1 ± 0.4 nM and immunoreactive fraction of 69.3 ± 0.9. Highest uptake of [67Cu]Cu-NOTA-trastuzumab was observed in JIMT-1 (33.9 ± 5.5% IA/g) and BT-474 (33.1 ± 10.6% IA/g) xenograft at 120 h post injection (p.i.). Effectiveness of the radioimmunoconjugate was also expressed as percent tumor growth inhibition (%TGI). [67Cu]Cu-NOTA-trastuzumab was more effective than trastuzumab against BT-474 xenografts (78% vs 54% TGI after 28 days), and JIMT-1 xenografts (90% vs 23% TGI after 19 days). Mean survival of [67Cu]Cu-NOTA-trastuzumab, trastuzumab and saline treated groups were > 90, 77 and 72 days for BT-474 xenografts, while that of JIMT-1 were 78, 24, and 20 days, respectively.

CONCLUSION

[67Cu]Cu-NOTA-trastuzumab is a promising theranostic agent against HER2-positive BC.

Efficacy of [67Cu]Cu-EB-TATE Theranostic Against Somatostatin Receptor Subtype-2-Positive Neuroendocrine Tumors

β--emitting 177Lu-octreotate is an approved somatostatin receptor subtype 2 (SSTR2)-directed peptide receptor radionuclide therapy for the treatment of gastroenteropancreatic neuroendocrine tumors (NETs). However,177Lu-octreotate has fast pharmacokinetics, requiring up to 4 treatment doses. Moreover, 177Lu is less than ideal for theranostics because of the low branching ratio of its γ-emissions, which limits its SPECT imaging capability. Compared with 177Lu, 67Cu has better decay properties for use as a theranostic. Here, we report the preclinical evaluation of a long-lived somatostatin analog, [67Cu]Cu-DOTA-Evans blue-TATE (EB-TATE), against SSTR2-positive NETs. Methods: The in vitro cytotoxicity of [67Cu]Cu-EB-TATE was investigated on 2-dimensional cells and 3-dimensional spheroids. In vivo pharmacokinetics and dosimetry were studied in healthy BALB/c mice, whereas ex vivo biodistribution, micro-SPECT/CT imaging, and therapy studies were done on athymic nude mice bearing QGP1.SSTR2 and BON1.SSTR2 xenografts. Therapeutic efficacy was compared with [177Lu]Lu-EB-TATE. Results: Projected human effective doses of [67Cu]Cu-EB-TATE for male (0.066 mSv/MBq) and female (0.085 mSv/MBq) patients are tolerable. In vivo micro-SPECT/CT imaging of SSTR2-positive xenografts with [67Cu]Cu-EB-TATE showed tumor-specific uptake and prolonged accumulation. Biodistribution showed tumor accumulation, with concurrent clearance from major organs over a period of 72 h. [67Cu]Cu-EB-TATE was more effective (60%) at eliminating tumors that were smaller than 50 mm3 within the first 15 d of therapy than was [177Lu]Lu-EB-TATE (20%) after treatment with 2 doses of 15 MBq administered 10 d apart. Mean survival of [67Cu]Cu-EB-TATE-treated groups was 90 d and more than 90 d, whereas that of [177Lu]Lu-EB-TATE was more than 90 d and 89 d against vehicle control groups (26 d and 53 d), for QGP1.SSTR2 and BON1.SSTR2 xenografts, respectively. Conclusion: [67Cu]Cu-EB-TATE exhibited high SSTR2-positive NET uptake and retention, with favorable dosimetry and SPECT/CT imaging capabilities. The antitumor efficacy of [67Cu]Cu-EB-TATE is comparable to that of [177Lu]Lu-EB-TATE, with [67Cu]Cu-EB-TATE being slightly more effective than [177Lu]Lu-EB-TATE for complete remission of small tumors. [67Cu]Cu-EB-TATE therefore warrants clinical development.

Preliminary PET Imaging of Microtubule-Based PET Radioligand [11C]MPC-6827 in a Nonhuman Primate Model of Alzheimer's Disease

The microtubule (MT) instability observed in Alzheimer's disease (AD) is commonly attributed to hyperphosphorylation of the MT-associated protein, tau. In vivo PET imaging offers an opportunity to gain critical information about MT changes with the onset and development of AD and related dementia. We developed the first brain-penetrant MT PET ligand, [11C]MPC-6827, and evaluated its in vivo imaging utility in vervet monkeys. Consistent with our previous in vitro cell uptake and in vivo rodent imaging experiments, [11C]MPC-6827 uptake increased with MT destabilization. Radioactive uptake was inversely related to (cerebrospinal fluid) CSF Aβ42 levels and directly related to age in a nonhuman primate (NHP) model of AD. Additionally, in vitro autoradiography studies also corroborated PET imaging results. Here, we report the preliminary results of PET imaging with [11C]MPC-6827 in four female vervet monkeys with high or low CSF Aβ42 levels, which have been shown to correlate with the Aβ plaque burden, similar to humans.

Biparatopic anti-HER2 drug radioconjugates as breast cancer theranostics

BACKGROUND

HER2 is overexpressed in 25-30% of breast cancer. Multiple domains targeting of a receptor can have synergistic/additive therapeutic effects.

METHODS

Two domain-specific ADCs trastuzumab-PEG6-DM1 (domain IV) and pertuzumab-PEG6-DM1 (domain II) were developed, characterised and radiolabeled to obtain [89Zr]Zr-trastuzumab-PEG6-DM1 and [67Cu]Cu-pertuzumab-PEG6-DM1 to study their in vitro (binding assay, internalisation and cytotoxicity) and in vivo (pharmacokinetics, biodistribution and immunoPET/SPECT imaging) characteristics.

RESULTS

The ADCs had an average drug-to-antibody ratio of 3. Trastuzumab did not compete with [67Cu]Cu-pertuzumab-PEG6-DM1 for binding to HER2. The highest antibody internalisation was observed with the combination of ADCs in BT-474 cells compared with single antibodies or ADCs. The combination of the two ADCs had the lowest IC50 compared with treatment using the single ADCs or controls. Pharmacokinetics showed biphasic half-lives with fast distribution and slow elimination, and an AUC that was five-fold higher for [89Zr]Zr-trastuzumab-PEG6-DM1 compared with [67Cu]Cu-pertuzumab-PEG6-DM1. Tumour uptake of [89Zr]Zr-trastuzumab-PEG6-DM1 was 51.3 ± 17.3% IA/g (BT-474), and 12.9 ± 2.1% IA/g (JIMT-1) which was similarly to [67Cu]Cu-pertuzumab-PEG6-DM1. Mice pre-blocked with pertuzumab had [89Zr]Zr-trastuzumab-PEG6-DM1 tumour uptakes of 66.3 ± 33.9% IA/g (BT-474) and 25.3 ± 4.9% IA/g (JIMT-1) at 120 h p.i.

CONCLUSION

Using these biologics simultaneously as biparatopic theranostic agents has additive benefits.

Mechanisms of ADC Toxicity and Strategies to Increase ADC Tolerability

Anti-cancer antibody-drug conjugates (ADCs) aim to expand the therapeutic index of traditional chemotherapy by employing the targeting specificity of monoclonal antibodies (mAbs) to increase the efficiency of the delivery of potent cytotoxic agents to malignant cells. In the past three years, the number of ADCs approved by the Food and Drug Administration (FDA) has tripled. Although several ADCs have demonstrated sufficient efficacy and safety to warrant FDA approval, the clinical use of all ADCs leads to substantial toxicity in treated patients, and many ADCs have failed during clinical development due to their unacceptable toxicity profiles. Analysis of the clinical data has demonstrated that dose-limiting toxicities (DLTs) are often shared by different ADCs that deliver the same cytotoxic payload, independent of the antigen that is targeted and/or the type of cancer that is treated. DLTs are commonly associated with cells and tissues that do not express the targeted antigen (i.e., off-target toxicity), and often limit ADC dosage to levels below those required for optimal anti-cancer effects. In this manuscript, we review the fundamental mechanisms contributing to ADC toxicity, we summarize common ADC treatment-related adverse events, and we discuss several approaches to mitigating ADC toxicity.

Simultaneous Imaging and Therapy Using Epitope-Specific Anti-Epidermal Growth Factor Receptor (EGFR) Antibody Conjugates

Matuzumab and nimotuzumab are anti-EGFR monoclonal antibodies that bind to different epitopes of domain III of EGFR. We developed ⁸⁹Zr-matuzumab as a PET probe for diagnosis/monitoring of response to treatment of a noncompeting anti-EGFR nimotuzumab antibody drug conjugate (ADC) using mouse colorectal cancer (CRC) xenografts. We developed ⁸⁹Zr-matuzumab and performed quality control in EGFR-positive DLD-1 cells. The K_D of matuzumab, DFO-matuzumab and ⁸⁹Zr-matuzumab in DLD-1 cells was 5.9, 6.2 and 3 nM, respectively. A competitive radioligand binding assay showed that ⁸⁹Zr-matuzumab and nimotuzumab bound to noncompeting epitopes of EGFR. MicroPET/CT imaging and biodistribution of ⁸⁹Zr-matuzumab in mice bearing EGFR-positive xenografts (HT29, DLD-1 and MDA-MB-231) showed high uptake that was blocked with pre-dosing with matuzumab but not with the noncompeting binder nimotuzumab. We evaluated nimotuzumab-PEG₆-DM1 ADC in CRC cells. IC₅₀ of nimotuzumab-PEG₆-DM1 in SNU-C2B, DLD-1 and SW620 cells was dependent on EGFR density and was up to five-fold lower than that of naked nimotuzumab. Mice bearing the SNU-C2B xenograft were treated using three 15 mg/kg doses of nimotuzumab-PEG₆-DM1, and ⁸⁹Zr-matuzumab microPET/CT was used to monitor the response to treatment. Treatment resulted in complete remission of the SNU-C2B tumor in 2/3 mice. Matuzumab and nimotuzumab are noncompeting and can be used simultaneously.

Improvement of Biosynthetic Ansamitocin P-3 Production Based on Oxygen-Vector Screening and Metabonomics Analysis

A novel approach involving exogenous oxygen vectors was developed for improving the production of biosynthetic Ansamitocin P-3 (AP-3). Four types of oxygen vectors including soybean oil, n-dodecane, n-hexadecane, and Tween-80 were applied to explore the effect of exogenous oxygen vectors on AP-3 yield. It was observed that soybean oil exhibited a better ability for promoting AP-3 generation than the other three oxygen vectors. Based on the results of the single-factor experiment, response surface methodology was employed to obtain the optimal soybean oil addition method. The optimum soybean oil concentration was 0.52%, and the addition time was 50 h. Under this condition, the yield of AP-3 reached 106.04 mg/L, which was 49.48% higher than that of the control group without adding oxygen vectors. To further investigate the influence of dissolved oxygen on precious orange tufts actinomycetes variety A. pretiosum strain metabolism and AP-3 yield, metabolomics analysis was carried out by detecting strain intermediate metabolites at various stages under different dissolved oxygen levels. Moreover, differential metabolite screening and metabolic pathway enrichment analysis were combined to exploit the effect mechanism of soybean oil on AP-3 production. Results suggested that primary metabolic levels of the TCA cycle and amino acid metabolism increased with the increase in dissolved oxygen level, which was beneficial to the life activities of bacteria and the synthesis of secondary metabolic precursors, thus increasing the production of AP-3.

Successful Application of CuAAC Click Reaction in Constructing 64Cu-Labeled Antibody Conjugates for Immuno-PET Imaging

Immuno-positron emission tomography (immuno-PET) is a rapidly growing imaging technique in which antibodies are radiolabeled to monitor their in vivo behavior in real time. However, effecting the controlled conjugation of a chelate-bearing radioactive atom to a bulky antibody without affecting its immunoreactivity at a specific site is always challenging. The in vivo stability of the radiolabeled chelate is also a key issue for successful tumor imaging. To address these points, a facile ultra-stable radiolabeling platform is developed by using the propylene cross-bridged chelator (PCB-TE2A-alkyne), which can be instantly functionalized with various groups via the click reaction, thus enabling specific conjugation with antibodies as per choice. The PCB-TE2A-tetrazine derivative is selected to demonstrate the proposed strategy. The antibody trastuzumab is functionalized with the trans-cyclooctene (TCO) moiety in the presence or absence of the PEG linker. The complementary ⁶⁴Cu-PCB-TE2A-tetrazine is synthesized via the click reaction and radiolabeled with ⁶⁴Cu ions, which then reacts with the aforementioned TCO-modified antibody via a rapid biorthogonal ligation. The ⁶⁴Cu-PCB-TE2A-trastuzumab conjugate is shown to exhibit excellent in vivo stability and to maintain a higher binding affinity toward HER2-positive cells. The tumor targeting feasibility of the radiolabeled antibody is evaluated in tumor models. Both ⁶⁴Cu-PCB-TE2A-trastuzumab conjugates show high tumor uptakes in biodistribution studies and enable unambiguous tumor visualization with minimum background noise in PET imaging. Interestingly, the ⁶⁴Cu-PCB-TE2A-PEG₄-trastuzumab containing an additional PEG linker displays a much faster body clearance compared to its counterpart with less PEG linker, thus affording vivid tumor imaging with an unprecedentedly high tumor-to-background ratio.

89Zr-Labeled Domain II-Specific scFv-Fc ImmunoPET Probe for Imaging Epidermal Growth Factor Receptor In Vivo

Simple Summary

Abundance of certain proteins such as epidermal growth factor receptor (EGFR) and their growth factors on cancer cells is in part responsible for their uncontrolled growth. Compounds that selectively bind to such proteins have diagnostic and/or therapeutic implications. EGFR has four binding domains (I-IV). Most anti-EGFR therapeutic antibodies bind to domain III. Compounds that bind to other domains have implications not only for diagnosis but also for monitoring therapy response. We describe the development of a diagnostic agent to be used with positron emission tomography (PET) that binds to domain II of EGFR. We developed ⁸⁹Zr-8709-scFv-Fc antibody PET agent and evaluated its binding characteristics in cancer cells and mouse models. The presence of a domain III-binding antibody such as nimotuzumab did not inhibit the binding of ⁸⁹Zr-8709-scFv-Fc, and vice versa. Therefore, ⁸⁹Zr-8709-scFv-Fc PET/CT can be used for diagnosis and monitoring therapy response in the presence of a domain III-binding agent.

Abstract

Epidermal growth factor receptor I (EGFR) is overexpressed in many cancers. The extracellular domain of EGFR has four binding epitopes (domains I- IV). All clinically approved anti-EGFR antibodies bind to domain III. Imaging agents that bind to domains other than domain III of EGFR are needed for accurate quantification of EGFR, patient selection for anti-EGFR therapeutics and monitoring of response to therapies. We recently developed a domain II-specific antibody fragment 8709. In this study, we have evaluated the in vitro and in vivo properties of ⁸⁹Zr-8709-scFv-Fc (105 kDa). We conjugated 8709-scFv-Fc with the deferoxamine (DFO) chelator and radiolabeled the DFO-8970-scFv with ⁸⁹Zr. We evaluated the binding of ⁸⁹Zr-DFO-8709-scFv-Fc in EGFR positive and negative cell lines DLD-1, MDA-MB-231 and MDA-MB-435, respectively, and in mouse xenograft models. Simultaneously, we have compared the binding of ⁸⁹Zr-8709-scFv-Fc with ¹¹¹In-nimotuzumab, a domain III anti-EGFR antibody. DFO-8709-scFv-Fc displayed similar cell binding specificity as 8709-scFv-Fc. Saturation cell binding assay and immunoreactive fraction showed that radiolabeling did not alter the binding of 8709-scFv-Fc. Biodistribution and microPET showed good uptake of ⁸⁹Zr-8709-scFv-Fc in xenografts after 120 h post injection (p.i). and was domain-specific to EGFR domain II. ⁸⁹Zr-8709-scFv-Fc did not compete for binding in vitro and in vivo with a known domain III binder nimotuzumab. The results show that ⁸⁹Zr-8709-scFv-Fc is specific to domain II of EGFR making it favorable for quantification of EGFR in vivo, hence, patient selection and monitoring of response to treatment with anti-EGFR antibodies.

Nimotuzumab Site-Specifically Labeled with 89Zr and 225Ac Using SpyTag/SpyCatcher for PET Imaging and Alpha Particle Radioimmunotherapy of Epidermal Growth Factor Receptor Positive Cancers

Simple Summary

Monoclonal antibodies (IgG) are excellent probes for targeting cell surface receptors for imaging and therapeutic applications. These theranostic agents are often developed by randomly conjugating radioisotopes/drugs/chelators to the primary amine of lysine or the sulfhydryl groups of cysteine on the antibody. Random conjugation often alters the properties of the antibody. We have site-specifically radiolabeled nimotuzumab an anti-epidermal growth factor receptor (EGFR) monoclonal antibody with 89Zr and 225Ac using SpyTag: ∆N-SpyCatcher for positron emission tomography (PET) imaging and alpha particle radiotherapy, and evaluated these agents in a model of EGFR-positive triple negative breast cancer (TNBC). Nimotuzumab-SpyTag-∆N-SpyCatcher constructs showed improved binding in vitro compared with randomly conjugated constructs. 89Zr-nimotuzumab-SpyTag-∆N-SpyCatcher specifically delineated EGFR-positive xenograft in vivo using microPET/CT imaging. Compared with control treatment groups, 225Ac-nimotuzumab-SpyTag-∆N-SpyCatcher more than doubled the survival of mice bearing EGFR-positive MDA-MB-231 TNBC xenograft. This work highlights a facile method to site-specifically radiolabel antibodies using SpyTag: ∆N-SpyCatcher.

Abstract

To develop imaging and therapeutic agents, antibodies are often conjugated randomly to a chelator/radioisotope or drug using a primary amine (NH₂) of lysine or sulfhydryl (SH) of cysteine. Random conjugation to NH₂ or SH groups can require extreme conditions and may affect target recognition/binding and must therefore be tested. In the present study, nimotuzumab was site-specifically labeled using ∆N-SpyCatcher/SpyTag with different chelators and radiometals. Nimotuzumab is a well-tolerated anti-EGFR antibody with low skin toxicities. First, ΔN-SpyCatcher was reduced using tris(2-carboxyethyl)phosphine (TCEP), which was followed by desferoxamine-maleimide (DFO-mal) conjugation to yield a reactive ΔN-SpyCatcher-DFO. The ΔN-SpyCatcher-DFO was reacted with nimotuzumab-SpyTag to obtain stable nimotuzumab-SpyTag-∆N-SpyCatcher-DFO. Radiolabeling was performed with ⁸⁹Zr, and the conjugate was used for the in vivo microPET imaging of EGFR-positive MDA-MB-468 xenografts. Similarly, ∆N-SpyCatcher was conjugated to an eighteen-membered macrocyclic chelator macropa-maleimide and used to radiolabel nimotuzumab-SpyTag with actinium-225 (²²⁵Ac) for in vivo radiotherapy studies. All constructs were characterized using biolayer interferometry, flow cytometry, radioligand binding assays, HPLC, and bioanalyzer. MicroPET/CT imaging showed a good tumor uptake of ⁸⁹Zr-nimotuzumab-SpyTag-∆N-SpyCatcher with 6.0 ± 0.6%IA/cc (n = 3) at 48 h post injection. The EC₅₀ of ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher and ²²⁵Ac-control-IgG-SpyTag-∆N-SpyCatcher against an EGFR-positive cell-line (MDA-MB-468) was 3.7 ± 3.3 Bq/mL (0.04 ± 0.03 nM) and 18.5 ± 4.4 Bq/mL (0.2 ± 0.04 nM), respectively. In mice bearing MDA-MB-468 EGFR-positive xenografts, ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher significantly (p = 0.0017) prolonged the survival of mice (64 days) compared to ²²⁵Ac-control IgG (28.5 days), nimotuzumab (28.5 days), or PBS-treated mice (30 days). The results showed that the conjugation and labeling using SpyTag/∆N-SpyCatcher to nimotuzumab did not significantly (p > 0.05) alter the receptor binding of nimotuzumab compared with a non-specific conjugation approach. ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher was effective in vitro and in an EGFR-positive triple negative breast cancer xenograft model.

Development and preclinical evaluation of cixutumumab drug conjugates in a model of insulin growth factor receptor I (IGF-1R) positive cancer

Overexpression of insulin growth factor receptor type 1 (IGF-1R) is observed in many cancers. Antibody drug conjugates (ADCs) with PEGylated maytansine (PEG₆-DM1) show promise in vitro. We developed PEG₆-DM1 ADCs with low and high drug to antibody ratios (DAR) using an anti-IGF-1R antibody cixutumumab (IMC-A12). Conjugates with low (cixutumumab-PEG₆-DM1-Low) and high (cixutumumab-PEG₆-DM1-High) DAR as 3.4 and 7.2, respectively, were generated. QC was performed by UV spectrophotometry, HPLC, bioanalyzer, and biolayer-interferometry. We compared the in vitro binding and internalization rates of the ADCs in IGF-1R-positive MCF-7/Her18 cells. We radiolabeled the ADCs with ¹¹¹In and used microSPECT/CT imaging and ex vivo biodistribution to understand their in vivo behavior in MCF-7/Her18 xenograft mice. The therapeutic potential of the ADC was studied in vitro and in mouse xenograft. Internalization rates of all ADCs was high and increased over 48 h and EC₅₀ was in the low nanomolar range. MicroSPECT/CT imaging and ex vivo biodistribution showed significantly lower tumor uptake of ¹¹¹In-cixutumumab-PEG₆-DM1-High compared to ¹¹¹In-cixutumumab-PEG₆-DM1-Low and ¹¹¹In-cixutumumab. Cixutumumab-PEG₆-DM1-Low significantly prolonged the survival of mice bearing MCF-7/Her18 xenograft compared with cixutumumab, cixutumumab-PEG₆-DM1-High, or the PBS control group. Cixutumumab-PEG₆-DM1-Low ADC was more effective. The study highlights the potential utility of cixutumumab-ADCs as theranostics against IGF-1R positive cancers.

Therapeutic Efficacy Evaluation of Pegylated Liposome Encapsulated With Vinorelbine Plus 111In Repeated Treatments in Human Colorectal Carcinoma With Multimodalities of Molecular Imaging

BACKGROUND/AIM

In precision therapy, liposomal encapsulated chemotherapeutic drugs have been developed to treat cancers by achieving higher drug accumulation in the tumor compared to normal tissues/organs.

MATERIALS AND METHODS

We developed a novel chemoradiotherapeutic approach via nanoliposomes conjugated with vinorelbine (VNB) and ¹¹¹In (¹¹¹In-VNB-liposome) and examined their pharmacokinetics, biodistribution, maximum tolerance dose, and toxicity in a NOD/SCID mouse model.

RESULTS

Pharmacokinetic results showed that the area under the curve (AUC) of PEGylated liposomes was about 17-fold higher than that of the free radioisotope. Tumor growth inhibition by ¹¹¹In-VNB-liposome was significantly higher than that of the control (p<0.05).

CONCLUSION

The tumors in NOD/SCID mice bearing HT-29/tk-luc xenografts were significantly suppressed by ¹¹¹In-VNB-liposomes. The study proposed repeated treatments with a novel liposome-mediated radiochemotherapy and validation of therapeutic efficacy via imaging.

Smart Targeting To Improve Cancer Therapeutics

Cancer is the second largest cause of death worldwide with the number of new cancer cases predicted to grow significantly in the next decades. Biotechnology and medicine can and should work hand-in-hand to improve cancer diagnosis and treatment efficacy. However, success has been frequently limited, in particular when treating late-stage solid tumors. There still is the need to develop smart and synergistic therapeutic approaches to achieve the synthesis of strong and effective drugs and delivery systems. Much interest has been paid to the development of smart drug delivery systems (drug-loaded particles) that utilize passive targeting, active targeting, and/or stimulus responsiveness strategies. This review will summarize some main ideas about the effect of each strategy and how the combination of some or all of them has shown to be effective. After a brief introduction of current cancer therapies and their limitations, we describe the biological barriers that nanoparticles need to overcome, followed by presenting different types of drug delivery systems to improve drug accumulation in tumors. Then, we describe cancer cell membrane targets that increase cellular drug uptake through active targeting mechanisms. Stimulus-responsive targeting is also discussed by looking at the intra- and extracellular conditions for specific drug release. We include a significant amount of information summarized in tables and figures on nanoparticle-based therapeutics, PEGylated drugs, different ligands for the design of active-targeted systems, and targeting of different organs. We also discuss some still prevailing fundamental limitations of these approaches, eg, by occlusion of targeting ligands.

Effectiveness and normal tissue toxicity of Auger electron (AE) radioimmunotherapy (RIT) with [111In]In-Bn-DTPA-nimotuzumab in mice with triple-negative or trastuzumab-resistant human breast cancer xenografts that overexpress EGFR

INTRODUCTION

Our objective was to evaluate the effectiveness and normal tissue toxicity of nimotuzumab labeled with the Auger electron (AE)-emitter, ¹¹¹In ([¹¹¹In]In-Bn-DTPA-nimotuzumab) for radioimmunotherapy (RIT) of human triple-negative breast cancer (TNBC) or trastuzumab-resistant HER2-positive BC tumors overexpressing epidermal growth factor receptors (EGFR) in athymic mice.

METHODS

Normal tissue toxicity was studied in non-tumor-bearing Balb/c mice i.v. administered 9.0 or 28.6 MBq (3 mg/kg) of [¹¹¹In]In-Bn-DTPA-nimotuzumab, unlabeled nimotuzumab (3 mg/kg) or normal saline. A complete blood cell count (CBC) and serum alanine aminotransferase (ALT) and creatinine (Cr) were measured at 14 days. Body weight was monitored. RIT studies were performed in CD-1 athymic mice engrafted s.c. with MDA-MB-468 human TNBC tumors or TrR1 HER2-positive but trastuzumab-resistant BC tumors. Mice were i.v. administered two amounts (15.5 MBq; 3 mg/kg) of [¹¹¹In]In-Bn-DTPA-nimotuzumab separated by 14 days. Control mice received unlabeled Bn-DTPA-nimotuzumab (3 mg/kg) or anti-HER2 [¹¹¹In]In-Bn-DTPA-trastuzumab or normal saline. Tumor growth and body weight were measured for 6 weeks. A tumor growth index (TGI) and body weight index (BWI) were calculated to compare the tumor size and body weight post-treatment with the pre-treatment values. A tumor doubling ratio (TDR) was calculated for each treatment group compared to control mice receiving normal saline.

RESULTS

There was no loss of body weight or decreased red blood cells (RBC) or platelets (PLT) or increased serum ALT or Cr in Balb/c mice administered 9.0 or 28.6 MBq (3 mg/kg) of [¹¹¹In]In-Bn-DTPA-nimotuzumab compared to mice treated with unlabeled Bn-DTPA-nimotuzumab (3 mg/kg) or normal saline. There was a significant decrease in white blood cell (WBC) counts in Balb/c mice receiving 28.6 MBq but not 9.0 MBq of [¹¹¹In]In-Bn-DTPA-nimotuzumab. Based on these results, an administered amount of 15.5 MBq (3 mg/kg) was selected for RIT studies. Administration of two amounts (15.5 MBq; 3 mg/kg) separated by 14 days to CD-1 athymic mice with s.c. MDA-MB-468 xenografts strongly inhibited tumor growth. The TDR for mice treated with [¹¹¹In]In-Bn-DTPA-nimotuzumab was 2.15 compared to control mice receiving normal saline. In contrast, treatment with unlabeled Bn-DTPA-nimotuzumab or [¹¹¹In]In-Bn-DTPA-trastuzumab had no significant effect on tumor growth (TDR = 0.96 and 1.08, respectively). RIT with [¹¹¹In]In-Bn-DTPA-nimotuzumab also strongly inhibited the growth of TrR1 tumors in athymic mice (TDR = 2.13) compared to unlabeled Bn-DTPA-nimotuzumab (TDR = 0.91). There were no losses in body weight over 6 weeks in tumor bearing mice receiving [¹¹¹In]In-Bn-DTPA-nimotuzumab, unlabeled Bn-DTPA-nimotuzumab, [¹¹¹In]In-Bn-DTPA-trastuzumab or normal saline.

CONCLUSIONS

[¹¹¹In]In-Bn-DTPA-nimotuzumab was effective for treatment of TNBC or trastuzumab-resistant HER2-positive human BC tumors in mice that overexpress EGFR at administered amounts that caused no decrease in body weight or normal tissue toxicity in non-tumor-bearing Balb/c mice.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

Our results suggest that Auger electron RIT with [¹¹¹In]In-Bn-DTPA-nimotuzumab may provide a novel therapeutic option for patients with TNBC or trastuzumab-resistant HER2-positive BC that overexpresses EGFR. The low normal tissue toxicity of this approach may allow combination with other targeted therapies such as antibody-drug conjugates (ADCs).

Development of an UPLC-MS/MS method coupled with in-source CID for quantitative analysis of PEG-PLA copolymer and its application to a pharmacokinetic study in rats

Poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) is a biocompatible and amphiphilic block copolymer composed of a hydrophilic PEG block and a hydrophobic PLA block, which can self-assemble into micelles in water. It is one of the most commonly used biodegradable polymers for drug encapsulation, drug solubilization and drug delivery. Due to the complexity and heterogeneity of PEG-PLA, the precise analysis of this polymer is a great challenge. This study reports an application of an UPLC tandem mass spectrometry coupled with in-source collision induced dissociation (CID) technique for the analysis of a model compound mPEG2000-PDLLA2500-COOH, which could be dissociated in source and generate a series of fragment ions corresponding to its subunits. These surrogate ions including PLA-specific and PEG-specific fragment ions could be further broken into specific product ions in collision cell. Finally, the ion transition at m/z 505.0 → 217.0 was selected for the quantitation of mPEG2000-PDLLA2500-COOH. This assay achieved a lower limit of quantitation (LLOQ) of 0.05 μg/mL with only 30 μL rat plasma. The linear range is 0.05 to 5 μg/mL. Intraday and interday accuracy and precision were within ±12.1%. The method was successfully applied to the pharmacokinetic study of mPEG2000-PDLLA2500-COOH in rats. The results revealed that LC-MS/MS coupled with in-source CID is a sensitive and specific strategy for analysis of PEG-PLA. This method can be potentially extended to the analysis of other pharmaceutical polymer excipients.