Background The efficacy of current bone-targeting agents, notably bisphosphonates, in the treatment of bone metastases remains limited by their systemic toxicity and excessively long half-life. This study aims to develop bone-targeting agents inspired by osteotropic peptides involved in the bone mineralization process. These agents are intended to provide an innovative alternative to bisphosphonates for precision bone targeting. Results Osteotropic peptides and phosphopeptides were obtained by solid-phase synthesis and conjugated to DOTA. The peptides were radiolabeled with gallium-68 or lutetium-177, and their binding affinity to bone was tested in vivo. Osteopontin and matrix extracellular phosphoglycoprotein (MEPE) derived peptides did not show strong binding to bone. Systematic variations in oligoglutamic acid chain length, as well as the positioning and clustering of phosphorylated serine residues, enabled the identification of an optimized phosphopeptide. Clustering phosphorylated sites within the peptide sequence provided significant advantages over phosphorylated moieties scattered throughout the peptide sequence. DOTA-pS(4)E(8) showed the strongest affinity for bone, comparable to the clinically used bone targeting agent methylene bisphosphonate (MBP). Conclusions The novel phosphopeptides match the outstanding bone-targeting capabilities of bisphosphonates and show comparable pharmacokinetics. Owing to their peptidic nature and the consequently anticipated favorable toxicological profile, these agents warrant further investigation as versatile bone-targeting vectors.

Nanobodies (Nbs) are considered promising antibody fragments for overcoming limitations in precision oncology due to their high specificity and deep tissue penetration. However, their therapeutic potential remains limited by their rapid renal clearance. In this study, anti-HER2 Nb-loaded liposomes with dual functionalization combining polyethylene glycol 2000 (PEG) and cyclic cell-penetrating peptides are developed to ameliorate their pharmacokinetic behavior while retaining binding specificity. Liposomal formulations with high encapsulation efficiencies are produced with dual centrifugation. Biophysical characterization reveals that PEGylation effectively mitigates cCPP-induced membrane destabilization, ensuring structural integrity. In vitro assays confirm that, despite the steric shielding by PEG, the encapsulated Nbs retain their functionality and specific binding to HER2-overexpressing cells. In vivo studies in zebrafish larvae demonstrate excellent biocompatibility and lack of immunogenicity. Crucially, liposomal encapsulation significantly modulates the pharmacokinetic profile of Nbs in rats, reducing renal accumulation compared to free Nbs. This study presents a robust liposomal platform that successfully balances the stealth properties of PEG with the functional benefits of cCPPs. Consequently, this platform offers an effective strategy to enhance the therapeutic window of low-molecular-weight biologics.

CD137 (4-1BB) is a surface marker selectively expressed on activated T cells, whose induction depends on antigen recognition, and is readily internalized upon ligand recognition. These factors make it an attractive target for antibody-drug conjugates (ADCs). Selective elimination of CD137+ T cells could represent a therapeutic strategy in autoimmune diseases, allograft rejection, and graft-versus-host disease. In this study, we aimed to generate and evaluate anti-human and anti-mouse CD137 ADCs for their ability to kill CD137-expressing cells. ADCs were produced from monoclonal antibodies by stochastic conjugation of active esters to lysine residues. The generated ADCs bound effectively and specifically to CD137 on stable Jurkat and HEK-293T transfectants, and were efficiently internalized. In transfectants expressing high CD137 surface levels, selective cytotoxicity was observed upon incubation with ADCs. Human and mouse T-cell blasts were generated in vitro with anti-CD3/anti-CD28-coated beads to evaluate killing using flow cytometry. However, despite testing different drug-to-antibody ratios (DARs), the ADCs failed to kill activated T-cell blasts of either human or murine origin, and they did not ameliorate experimental graft-versus-host disease in mice. These findings demonstrate that although anti-CD137 ADCs can be successfully engineered to bind and internalize into CD137+ cells, the evaluated approaches did not achieve therapeutic elimination of pathogenic T lymphocytes.

The benefit that antibiotics confer to the welfare of mankind is threatened by bacterial resistance. Resistance to daptomycin, a cyclic lipopeptide frequently used for the treatment of complicated bacteremia, is a prime example of this alarming situation. As the restricted number of antibacterial drug targets limits de novo development, chemical modification of existing compounds represents an alternative development option for future antimicrobials. This approach involves altering compounds to target bacteria through multiple mechanisms and/or to reinforce them against resistant strains. Herein, the conjugation of polycationic peptides to daptomycin enhances its effectiveness against a highly daptomycin-resistant laboratory strain of Staphylococcus aureus and clinical isolates of Enterococcus faecium with reduced daptomycin sensitivity. Notably, unlike daptomycin, the activity of these conjugates does not necessarily depend on the calcium concentration. In addition to regaining bacteriolytic activity, the findings indicate the acquisition of an additional or amended mode of action as evidenced by pore formation and the disruption of membrane potential. The combination of enhanced in vitro potency, in vivo activity, and tolerability highlights the potential of this drug modification strategy in combating multidrug-resistant bacteria.

Antibiotic resistance still represents a global health concern which diminishes the pool of effective antibiotics. With the vancomycin derivative FU002, we recently reported a highly potent substance active against Gram-positive bacteria with the potential to overcome vancomycin resistance. However, the translation of its excellent antimicrobial activity into clinical efficiency could be hampered by its rapid elimination from the blood stream. To improve its pharmacokinetics, we encapsulated FU002 in PEGylated liposomes. For PEG-liposomal FU002, no relevant cytotoxicity on liver, kidney and red blood cells was observed. Studies in Wistar rats revealed a significantly prolonged blood circulation of the liposomal antibiotic. In microdilution assays it could be demonstrated that encapsulation does not diminish the antimicrobial activity against staphylococci and enterococci. Highlighting its great potency, liposomal FU002 exhibited a superior therapeutic efficacy when compared to the free form in a Galleria mellonella larvae infection model.

Radiopharmaceutical therapies (RPTs) based on fibroblast activation protein (FAP) and FAP inhibitors (FAPIs) are a new option for progressive metastatic cancer in patients pretreated multiple times. To date, published in-human data refer to initial experiences with β-emitting 90Y- and 177Lu-based RPT. However, the short tumor retention time of FAPI ligands is considered a major limitation of FAPI RPT. Therefore, fractionated FAPI RPT with 213Bi, an α-emitter with a half-life of 46 min, appears to be a promising FAPI RPT regimen. Here, we report on our initial experiences with regard to the feasibility, tolerability, and response of fractionated 213Bi-FAPI-46 RPT. Methods: Six patients (4 women and 2 men) with progressive metastatic solid tumors (3 colon cancer, 1 anal cancer, 1 breast cancer, and 1 prostate cancer) aged 16-77 y were treated with a mean of 1,609 MBq of 213Bi-FAPI-46, fractionated into 53 single applications (range, 5-12 RPT applications per patient; mean, 8.8 applications) over a period of up to 107 h per patient. Of the 6 patients, 4 patients received adjuvant treatment with pembrolizumab. 18F-FDG (4 patients) and 68Ga-FAPI-46 (5 patients) PET/CT scans were performed before and after RPT. PET images were assessed visually and by calculating total lesion glycolysis and total lesion FAPI. Results: RPT with 213Bi-FAPI-46 was well tolerated without adverse side effects. In terms of visual response assessment, there was 1 partial response (16.7%), 1 patient with stable disease (16.7%), and 4 patients with progressive disease (66.7%). Concordantly, total lesion glycolysis and total lesion FAPI were decreased in the responding patient (not applicable and -24.3%, respectively), slightly decreased in the patient with stable disease (-10.6% and -5.9%, respectively), and increased in the 4 patients with progression (mean, +104.4% and +321.3%, respectively). Conclusion: Fractionated FAPI RPT with the short-half-life α-emitter 213Bi-FAPI-46 is a promising approach that matches the pharmacokinetics of FAPI-46 better than the 177Lu- or 90Y-labeled compounds. In this pilot project, fractionated RPT with 213Bi-FAPI-46 showed good clinical tolerability and even led to regressive or stable disease in the short term in 2 of 6 patients. Further studies with larger patient cohorts are required to evaluate the actual efficacy and long-term effects of this variant of FAPI RPT.

Antibiotic-resistant enterococci represent a significant global health challenge. Unfortunately, most β-lactam antibiotics are not applicable for enterococcal infections due to intrinsic resistance. To extend their antimicrobial spectrum, polycationic peptides are conjugated to examples from each of the four classes of β-lactam antibiotics. Remarkably, the β-lactam-peptide conjugates gained an up to 1000-fold increase in antimicrobial activity against vancomycin-susceptible and vancomycin-resistant enterococci. Even against β-lactam-resistant Gram-negative strains, the conjugates are found to be effective despite their size exceeding the exclusion volume of porins. The extraordinary gain of activity can be explained by an altered mode of killing. Of note, the conjugates showed a concentration-dependent activity in contrast to the parent β-lactam antibiotics that exhibited a time-dependent mode of action. In comparison to the parent β-lactams, the conjugates showed altered affinities to the penicillin-binding proteins. Furthermore, it is found that peptide conjugation also resulted in a different elimination route of the compounds when administered to rodents. In mice systemically infected with vancomycin-resistant enterococci, treatment with a β-lactam-peptide conjugate reduced bacterial burden in the liver compared to its originator. Therefore, peptide modification of β-lactam antibiotics represents a promising platform strategy to broaden their efficacy spectrum, particularly against enterococci.

Induction of tolerance can be achieved with Modified Immune Cells (MIC) by infusion of mononuclear cells challenged with mitomycin C (MMC). Although MIC treatment has been successful in several animal models for autoimmunity and in clinical studies of solid organ transplantation, the mechanism of immunosuppression is not fully elucidated. In lupus nephritis, the glomerular deposition of immune complexes is associated with accumulating immune cells in the kidney. The infiltrating immune cells frequently establish tertiary lymphoid structures (TLS) supporting adaptive autoimmune responses toward locally displayed antigens. Since TLS display a high persistence to peripheral B cell depletion, the destruction of TLS presents an essential treatment goal in lupus nephritis. In this study, we used lupus nephritis prone NZB/W F1 mice to show the destruction of TLS in the kidney after MIC treatment. Independent of treatment, >86% of animals displayed dense lymphocytic aggregates proximal to the pelvic wall of the medulla and the arcuate arteries within the cortex of kidneys. Cell type composition of TLS changed drastically after MIC treatment leading to diminished B-cells, a decreased B-cell/T-cell ratio, and a T cell dominated phenotype. Furthermore, a loss of organization of the TLS was observed after MIC treatment. The strict separation of B-cell and T-cell areas was abrogated, and germinal centers were disintegrated. However, regulatory T-cells remained unchanged indicative of a B-cell centric treatment mechanism. Our data provides a putative in vivomechanism how MIC treatment inhibits progression of active lupus nephritis by the destruction of tertiary lymphoid structures within the kidney. Commercial Support - TolerogenixX GmbH

Significance Statement In previous work, the authors demonstrated that kidney transplant recipients developed donor-specific unresponsiveness when they were given a pretransplant infusion of modified donor-derived PBMCs. In this study, they provide evidence that the immunosuppressive properties of these cells persist and the donor-specific unresponsiveness is long-lasting. In the four patients who received the highest dose of the modified immune cells, administration of these cells was associated with a striking increase in IL-10–producing regulatory B lymphocytes and evidence of the consensus gene expression signature of operational tolerance. In vitro , donor-specific unresponsiveness was abolished after B lymphocyte depletion, suggesting a direct pathophysiologic role for regulatory B lymphocytes. These findings support the notion that modified donor-derived PBMCs may be useful in kidney transplantation, but this approach requires further validation and rigorous controlled randomized studies. Background We recently demonstrated that donor-derived modified immune cells (MICs)—PBMCs that acquire immunosuppressive properties after a brief treatment—induced specific immunosuppression against the allogeneic donor when administered before kidney transplantation. We found up to a 68-fold increase in CD19 + CD24 hi CD38 hi transitional B lymphocytes compared with transplanted controls. Methods Ten patients from a phase 1 clinical trial who had received MIC infusions before kidney transplantation were followed to post-transplant day 1080. Results Patients treated with MICs had a favorable clinical course, showing no donor-specific human leukocyte antigen antibodies or acute rejections. The four patients who had received the highest dose of MICs 7 days before surgery and were on reduced immunosuppressive therapy showed an absence of in vitro lymphocyte reactivity against stimulatory donor blood cells, whereas reactivity against third party cells was preserved. In these patients, numbers of transitional B lymphocytes were 75-fold and seven-fold higher than in 12 long-term survivors on minimal immunosuppression and four operationally tolerant patients, respectively ( P <0.001 for both). In addition, we found significantly higher numbers of other regulatory B lymphocyte subsets and a gene expression signature suggestive of operational tolerance in three of four patients. In MIC-treated patients, in vitro lymphocyte reactivity against donor blood cells was restored after B lymphocyte depletion, suggesting a direct pathophysiologic role of regulatory B lymphocytes in donor-specific unresponsiveness. Conclusions These results indicate that donor-specific immunosuppression after MIC infusion is long-lasting and associated with a striking increase in regulatory B lymphocytes. Donor-derived MICs appear to be an immunoregulatory cell population that when administered to recipients before transplantation, may exert a beneficial effect on kidney transplants. Clinical Trial registry name and registration number: MIC Cell Therapy for Individualized Immunosuppression in Living Donor Kidney Transplant Recipients (TOL-1), NCT02560220

Background:The administration of modified immune cells (MIC) before kidney transplantation led to specific immunosuppression against the allogeneic donor and a significant increase in regulatory B lymphocytes. We wondered how this approach affected the continued clinical course of these patients.Methods:Ten patients from a phase I clinical trial who had received MIC infusions prior to kidney transplantation were retrospectively compared to 15 matched standard-risk recipients. Follow-up was until year five after surgery.Results:The 10 MIC patients had an excellent clinical course with stable kidney graft function, no donor-specific human leukocyte antigen antibodies (DSA) or acute rejections, and no opportunistic infections. In comparison, a retrospectively matched control group receiving standard immunosuppressive therapy had a higher frequency of DSA (log rank P = 0.046) and more opportunistic infections (log rank P = 0.033). Importantly, MIC patients, and in particular the four patients who had received the highest cell number 7 days before surgery and received low immunosuppression during follow-up, continued to show a lack of anti-donor T lymphocyte reactivity in vitro and high CD19+CD24hiCD38hi transitional and CD19+CD24hiCD27+ memory B lymphocytes until year five after surgery.Conclusions:MIC infusions together with reduced conventional immunosuppression were associated with good graft function during five years of follow-up, no de novo DSA development and no opportunistic infections. In the future, MIC infusions might contribute to graft protection while reducing the side effects of immunosuppressive therapy. However, this approach needs further validation in direct comparison with prospective controls.Trial registration:https://clinicaltrials.gov/, identifier NCT02560220 (for the TOL-1 Study). EudraCT Number: 2014-002086-30.

Introduction Donor-derived modified immune cells (MIC) induced long-term specific immunosuppression against the allogeneic donor in preclinical models of transplantation. In a phase I clinical trial (TOL-1 Study), MIC treatment resulted in a cellular phenotype that was directly and indirectly suppressive to the recipient’s immune system allowing for reduction of conventional immunosuppressive therapy. Here, we describe a protocol for a randomised controlled, multicentre phase-IIb clinical trial of individualised immunosuppression with intravenously administered donor MIC compared with standard-of-care (SoC) in living donor kidney transplantation (TOL-2 Study). Methods and analysis Sixty-three living donor kidney transplant recipients from six German transplant centres are randomised 2:1 to treatment with MIC (MIC group, N=42) or no treatment with MIC (control arm, N=21). MIC are manufactured from donor peripheral blood mononuclear cells under Good Manufacturing Practice conditions. The primary objective of this trial is to determine the efficacy of MIC treatment together with reduced conventional immunosuppressive therapy in terms of achieving an operational tolerance-like phenotype compared with SoC 12 months after MIC administration. Key secondary endpoints are the number of patient-relevant infections as well as a composite of biopsy-proven acute rejection, graft loss, graft dysfunction or death. Immunosuppressive therapy of MIC-treated patients is reduced during follow-up under an extended immunological monitoring including human leucocyte antigen-antibody testing, and determination of lymphocyte subsets, for example, regulatory B lymphocytes (Breg) and antidonor T cell response. A Data Safety Monitoring Board has been established to allow an independent assessment of safety and efficacy. Ethics and dissemination Ethical approval has been provided by the Ethics Committee of the Medical Faculty of the University of Heidelberg, Heidelberg, Germany (AFmu-580/2021, 17 March 2022) and from the Federal Institute for Vaccines and Biomedicines, Paul-Ehrlich-Institute, Langen, Germany (Vorlage-Nr. 4586/02, 21 March 2022). Written informed consent will be obtained from all patients and respective donors prior to enrolment in the study. The results from the TOL-2 Study will be published in peer-reviewed medical journals and will be presented at symposia and scientific meetings. Trial registration number NCT05365672.

ABSTRACT:Prostate-specific membrane antigen (PSMA) PET/CT is a highly reliable nuclear tracer for diagnostic imaging of prostate cancer. However, PSMA is also expressed by some nonprostatic tissues such as benign tumors, inflammatory processes, and malignant neoplasms. This case presents a patient with prostate cancer and follicular lymphoma undergoing PSMA PET/CT. Remarkably, both tumor entities were clearly detected in the scan. Yet, the 2 malignancies demonstrated rather different ranges in terms of SUVmax uptake values and therefore still enabled precise and accurate discrimination of prostate cancer and follicular lymphoma.

Adoptive cell therapy with NY-ESO-1-specific T cells is a promising option for the treatment of soft tissue sarcoma (STS) but achieves only transient tumor control in the majority of cases. A strategy to optimize this cell therapeutic approach might be the modulation of the expression of the cancer-testis antigen NY-ESO-1 using histone deacetylase inhibitors (HDACis). In this study, the ex vivo effect of combining NY-ESO-1-specific T cells with the clinically approved pan HDACis panobinostat or vorionstat was investigated. Our data demonstrated that STS cells were sensitive to HDACis. Administration of HDACi prior to NY-ESO-1-specific T cells exerted enhanced lysis against the NY-ESO-1+ STS cell line SW982. This correlated with an increase in the NY-ESO-1 and HLA-ABC expression of SW982 cells, as well as increased CD25 expression on NY-ESO-1-specific T cells. Furthermore, the immune reactivity of NY-ESO-1-specific CD8+ T cells in terms of cytokine release was enhanced by HDACis. In summary, pretreatment with HDACis represents a potential means of enhancing the cytotoxic efficacy of NY-ESO-1-specific T cells against NY-ESO-1-positive STS.

As multidrug-resistant bacteria represent a concerning burden, experts insist on the need for a dramatic rethinking on antibiotic use and development in order to avoid a post-antibiotic era. New and rapidly developable strategies for antimicrobial substances, in particular substances highly potent against multidrug-resistant bacteria, are urgently required. Some of the treatment options currently available for multidrug-resistant bacteria are considerably limited by side effects and unfavorable pharmacokinetics. The glycopeptide vancomycin is considered an antibiotic of last resort. Its use is challenged by bacterial strains exhibiting various types of resistance. Therefore, in this study, highly active polycationic peptide-vancomycin conjugates with varying linker characteristics or the addition of PEG moieties were synthesized to optimize pharmacokinetics while retaining or even increasing antimicrobial activity in comparison to vancomycin. The antimicrobial activity of the novel conjugates was determined by microdilution assays on susceptible and vancomycin-resistant bacterial strains. VAN1 and VAN2, the most promising linker-modified derivatives, were further characterized in vivo with molecular imaging and biodistribution studies in rodents, showing that the linker moiety influences both antimicrobial activity and pharmacokinetics. Encouragingly, VAN2 was able to undercut the resistance breakpoint in microdilution assays on vanB and vanC vancomycin-resistant enterococci. Out of all PEGylated derivatives, VAN:PEG1 and VAN:PEG3 were able to overcome vanC resistance. Biodistribution studies of the novel derivatives revealed significant changes in pharmacokinetics when compared with vancomycin. In conclusion, linker modification of vancomycin-polycationic peptide conjugates represents a promising strategy for the modulation of pharmacokinetic behavior while providing potent antimicrobial activity.

Prostate-specific membrane antigen (PSMA) binding tracers are promising agents for the targeting of prostate tumors. To further optimize the clinically established radiopharmaceutical PSMA-617, novel PSMA ligands for prostate cancer endoradiotherapy were developed. A series of PSMA binding tracers that comprise a benzyl group at the chelator moiety were obtained by solid-phase synthesis. The compounds were labeled with 68Ga or 177Lu. Competitive cell-binding assays and internalization assays were performed using the cell line C4-2, a subline of the PSMA positive cell line LNCaP (human lymph node carcinoma of the prostate). Positron emission tomography (PET) imaging and biodistribution studies were conducted in a C4-2 tumor bearing BALB/c nu/nu mouse model. All 68Ga-labeled ligands were stable in human serum over 2 h; 177Lu-CA030 was stable over 72 h. The PSMA ligands revealed inhibition potencies [Ki] (equilibrium inhibition constants) between 4.8 and 33.8 nM. The percentage of internalization of the injected activity/106 cells of 68Ga-CA028, 68Ga-CA029, and 68Ga-CA030 was 41.2 ± 2.7, 44.3 ± 3.9, and 53.8 ± 5.4, respectively; for the comparator 68Ga-PSMA-617, 15.5 ± 3.1 was determined. Small animal PET imaging of the compounds showed a high tumor-to-background contrast. Organ distribution studies revealed high specific uptake in the tumor, that is, approximately 34.4 ± 9.8% of injected dose per gram (%ID/g) at 1 h post injection for 68Ga-CA028. At 1 h p.i., 68Ga-CA028 and 68Ga-CA030 demonstrated lower kidney uptake than 68Ga-PSMA-617, but at later time points, kidney time–activity curves converge. In line with the preclinical data, first diagnostic PET imaging using 68Ga-CA028 and 68Ga-CA030 revealed high-contrast detection of bone and lymph node lesions in patients with metastatic prostate cancer. The novel PSMA ligands, in particular CA028 and CA030, are promising agents for targeting PSMA-positive tumor lesions as shown in the preclinical evaluation and in a first patient, respectively. Thus, clinical translation of 68Ga-CA028 and 68Ga/177Lu-CA030 for diagnostics and endoradiotherapy of prostate cancer in larger cohorts of patients is warranted.

Chimeric antigen receptor (CAR) T cells directed against CD19 (CD19.CAR T cells) have yielded impressive clinical responses in the treatment of patients with lymphoid malignancies. However, resistance and/or relapse can limit treatment outcome. Risk of tumor escape can be reduced by combining treatment strategies. Selective inhibitors of nuclear export (SINEs) directed against nuclear exportin-1 (XPO1) have demonstrated anti-tumor efficacy in several hematological malignancies. The aim of the present study was to evaluate the combination of CAR T cells with the SINE compounds eltanexor and selinexor. As expected, eltanexor and selinexor were toxic to CD19-positive malignant cells and the sensitivity of cells towards SINEs correlated with the levels of XPO1-expression in ALL cell lines. When SINEs and CAR T cells were simultaneously combined, SINEs exerted toxicity towards CAR T cells and impaired their function affecting cytotoxicity and cytokine release ability. Flow cytometry and western blot analysis revealed that eltanexor decreased the cytoplasmic concentration of the transcription factor phosphorylated-STAT3 in CAR T cells. Due to CAR T-cell toxicity, sequential use of SINEs and CAR T cells was evaluated: Cytotoxicity of CAR T cells increased significantly when target cells were pre-treated with the SINE compound eltanexor. In addition, exhaustion of CAR T cells decreased when target cells were pre-treated with eltanexor. In summary, whereas the concomitant use of SINEs and CAR T cells does not seem advisable, sequential use of SINEs and CAR T cells might improve the anti-tumor efficacy of CAR T cells.

Spontaneous or operational tolerance is a phenomenon that rarely occurs in nature. By establishing a permanent "artificial" chimerism in a transplant recipient, tolerance to the specific donor can be reliably established; however, this comes at the price of a costly and burdensome induction therapy and the risk of developing graft-versus-host disease. Newer approaches with so-called advanced therapy medicinal products (ATMP) rely only on a short-term chimerism, which leads to a permanent graft acceptance via the increase of regulatory cell populations. In this context, therapy with regulatory T cells seem to be promising and these can possibly be further improved in the future by introducing a chimeric antigen receptor, so-called A2-CAR-Treg (regulatory T cells). Another approach represents therapy with modified immune cells (MIC) starting from monocytes. In the recipient these cells lead to a reduction of the donor-specific T cell response and to the formation of regulatory B lymphocytes. Ideally, regulatory cell products will in the future be able to reduce or completely replace drug-induced immunosuppression in transplantation and autoimmune diseases. Regulatory B lymphocytes appear to play an important role in the context of establishing durable transplant acceptance.