Peptide Optimization and Conjugation Strategies in the Development of Molecularly Targeted Magnetic Resonance Imaging Contrast Agents

Kolodziej, Andrew F.; Zhang, Zhaoda; Overoye-Chan, Kirsten; Jacques, Vincent; Caravan, Peter

doi:10.1007/978-1-62703-673-3_13

Cited by 19 publications

(17 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since AcM2pepBiotin shows trends of slightly reduced binding compared with M2pepBiotin (Fig 1 D), we investigated the effect of introducing an arginine (R0) at the start of the AcM2pep(RY)Biotin sequence to offset for loss in amine from acetylation of M2pep. In addition, we also substituted P5 with hydroxyproline (HyP), which has been shown previously to improve binding activity of another proline-containing peptide 31 . Both analogs were synthesized with the Y12y substitution, and binding study was evaluated in comparison to the Y12y analog.…”

Section: Resultsmentioning

confidence: 99%

Serum Stability and Affinity Optimization of an M2 Macrophage-Targeting Peptide (M2pep)

et al. 2016

View full text Add to dashboard Cite

Tumor associated macrophages (TAMs) are a major stromal component of the tumor microenvironment in several cancers. TAMs are a potential target for adjuvant cancer therapies due to their established roles in promoting proliferation of cancer cells, angiogenesis, and metastasis. We previously discovered an M2 macrophage-targeting peptide (M2pep) which was successfully used to target and deliver a pro-apoptotic KLA peptide to M2-like TAMs in a CT-26 colon carcinoma model. However, the effectiveness of in vivo TAM-targeting using M2pep is limited by its poor serum stability and low binding affinity. In this study, we synthesized M2pep derivatives with the goals of increasing serum stability and binding affinity. Serum stability evaluation of M2pepBiotin confirmed its rapid degradation attributed to exolytic cleavage from the N-terminus and endolytic cleavages at the W10/W11 and S16/K17 sites. N-terminal acetylation of M2pepBiotin protected the peptide against the exolytic degradation while W10w and K(17,18,19)k substitutions were able to effectively protect endolytic degradation at their respective cleavage sites. However, no tested amino acid changes at the W10 position resulted in both protease resistance at that site and retention of binding activity. Therefore, cyclization of M2pep was investigated. Cyclized M2pep better resisted serum degradation without compromising binding activity to M2 macrophages. During the serum stability optimization process, we also discovered that K9R and W10Y substitutions significantly enhanced binding affinity of M2pep. In an in vitro binding study of different M2pep analogs pre-incubated in mouse serum, cyclic M2pep with K9R and W10Y modifications (cyclic M2pep(RY)) retained the highest binding activity to M2 macrophages over time due to its improved serum stability. Finally, we evaluated the in vivo accumulation of sulfo-Cy5-labeled M2pep and cyclic M2pep(RY) in both the CT-26 and 4T1 breast carcinoma models. Cyclic M2pep(RY) outperformed M2pep in both tumor localization and selective accumulation in M2-like TAMs. In conclusion, we report cyclic M2pep(RY) as our lead M2pep analog with improved serum stability and M2 macrophage-binding activity. Its enhanced utility as an in vivo M2-like-TAM-targeting agent was demonstrated in two tumor models, and is expected to be applicable for other tumor models or in models of M2 macrophage-related diseases.

show abstract

Section: Resultsmentioning

confidence: 99%

Serum Stability and Affinity Optimization of an M2 Macrophage-Targeting Peptide (M2pep)

et al. 2016

View full text Add to dashboard Cite

show abstract

“…To confirm specificity for fibrin we first injected the non-binding probe 64 Cu-D-Cys-FBP8 in rats after mural carotid thrombosis. This probe is identical to 64 Cu-FBP8 except that one of the cysteines has its chirality inverted which abrogates fibrin binding (20). PET imaging showed no uptake in the thrombus (Figure 4A).…”

Section: Resultsmentioning

confidence: 99%

Multimodal Molecular Imaging Reveals High Target Uptake and Specificity of ¹¹¹In- and ⁶⁸Ga-Labeled Fibrin-Binding Probes for Thrombus Detection in Rats

et al. 2015

Self Cite

View full text Add to dashboard Cite

We recently showed the high target specificity and favorable imaging properties of 64Cu and Al18F positron emission tomography (PET) probes for non-invasive imaging of thrombosis. Here, our aim was to evaluate new derivatives labeled with either with 68Ga, 111In, or 99mTc as thrombus imaging agents for PET and single-photon emission computed tomography (SPECT). In this study, the feasibility and potential of these probes for thrombus imaging was assessed in detail in two animal models of arterial thrombosis. The specificity of the probes was further evaluated using a triple-isotope approach with multimodal SPECT/PET/CT imaging. Methods Radiotracers were synthesized using a known fibrin-binding peptide conjugated to NODAGA, DOTA-MA, or a diethylenetriamine ligand (DETA-PA), followed by labeling with 68Ga (FBP14, 68Ga-NODAGA), 111In (FBP15, 111In-DOTA-MA) or 99mTc (FBP16, 99mTc(CO)3-DETA-PA), respectively. PET or SPECT imaging, biodistribution, pharmacokinetics and metabolic stability were evaluated in rat models of mural and occlusive carotid artery thrombosis. In vivo target specificity was evaluated by comparing the distribution of the SPECT and PET probes with preformed 125I-labeled thrombi and with a non-binding control probe using SPECT/PET/CT imaging. Results All three radiotracers showed similar affinity to soluble fibrin fragment DD(E) (Ki = 0.53–0.83 μM). After the kidneys, the highest uptake of 68Ga-FBP14 and 111In-FBP15 was in the thrombus (1.0 ± 0.2% ID/g) with low off-target accumulation. Both radiotracers underwent fast systemic elimination (t1/2 = 8-15 min) through the kidneys, which led to highly conspicuous thrombi on PET and SPECT images. 99mTc-FBP16 displayed low target uptake and distribution consistent with aggregation and/or degradation. Triple isotope imaging experiments showed that both 68Ga-FBP14 and 111In-FBP15, but not the nonbinding derivative 64Cu-D-Cys-FBP8, detected the location of the 125I-labeled thrombus, confirming high target specificity. Conclusion 68Ga-FBP14 and 111In-FBP15 have high fibrin affinity and thrombus specificity, and represent useful PET and SPECT probes for thrombus detection.

show abstract

“…The fibrin-binding peptide used here was previously identified using phage display and was found to have two binding sites per fibrin monomer, which is attributed to the dimeric structure of fibrin (17, 18). Although the binding sites are still unknown, this peptide does not induce fibrinogen self-association and does not inhibit fibrin formation and thus minimizes the possibility of thrombosis or exacerbated bleeding after intravenous injection.…”

Section: Discussionmentioning

confidence: 99%

A synthetic fibrin cross-linking polymer for modulating clot properties and inducing hemostasis

et al. 2015

View full text Add to dashboard Cite

Clotting factor replacement is the standard management of acute bleeding in congenital and acquired bleeding disorders. We present a synthetic approach to hemostasis using an engineered hemostatic polymer (PolySTAT) that circulates innocuously in the blood, identifies sites of vascular injury, and promotes clot formation to stop bleeding. PolySTAT induces hemostasis by crosslinking the fibrin matrix within clots, mimicking the function of the transglutaminase Factor XIII. Furthermore, synthetic PolySTAT binds specifically to fibrin monomers and is uniformly integrated into fibrin fibers during fibrin polymerization, resulting in a fortified, hybrid polymer network with enhanced resistance to enzymatic degradation. In vivo hemostatic activity was confirmed in a rat model of trauma and fluid resuscitation in which intravenous administration of PolySTAT improved survival by reducing blood loss and resuscitation fluid requirements. PolySTAT-induced fibrin crosslinking is a novel approach to hemostasis utilizing synthetic polymers for non-invasive modulation of clot architecture with potentially wide-ranging therapeutic applications.

show abstract

Peptide Optimization and Conjugation Strategies in the Development of Molecularly Targeted Magnetic Resonance Imaging Contrast Agents

Cited by 19 publications

References 33 publications

Serum Stability and Affinity Optimization of an M2 Macrophage-Targeting Peptide (M2pep)

Serum Stability and Affinity Optimization of an M2 Macrophage-Targeting Peptide (M2pep)

Multimodal Molecular Imaging Reveals High Target Uptake and Specificity of ¹¹¹In- and ⁶⁸Ga-Labeled Fibrin-Binding Probes for Thrombus Detection in Rats

A synthetic fibrin cross-linking polymer for modulating clot properties and inducing hemostasis

Contact Info

Product

Resources

About

Peptide Optimization and Conjugation Strategies in the Development of Molecularly Targeted Magnetic Resonance Imaging Contrast Agents

Cited by 19 publications

References 33 publications

Serum Stability and Affinity Optimization of an M2 Macrophage-Targeting Peptide (M2pep)

Serum Stability and Affinity Optimization of an M2 Macrophage-Targeting Peptide (M2pep)

Multimodal Molecular Imaging Reveals High Target Uptake and Specificity of 111In- and 68Ga-Labeled Fibrin-Binding Probes for Thrombus Detection in Rats

A synthetic fibrin cross-linking polymer for modulating clot properties and inducing hemostasis

Contact Info

Product

Resources

About

Multimodal Molecular Imaging Reveals High Target Uptake and Specificity of ¹¹¹In- and ⁶⁸Ga-Labeled Fibrin-Binding Probes for Thrombus Detection in Rats