Prediction of Response to 177Lu-PSMA Therapy Based on Tumor-to-Kidney Ratio on Pretherapeutic PSMA PET/CT and Posttherapeutic Tumor-Dose Evaluation in mCRPC.

The aim of this study was to analyze the absorbed dose of 177Lu-PSMA in osseous versus lymphatic metastases in patients with metastatic castration-resistant prostate cancer across therapy cycles and to relate those data to therapeutic success. In addition, pretherapeutic prostate-specific membrane antigen (PSMA) PET/CT was evaluated for its ability to predict response behavior. Methods: The study comprised 30 patients with metastatic castration-resistant prostate cancer, each receiving at least 3 cycles of 177Lu-PSMA therapy. Prostate-specific antigen (PSA) values between baseline and 6 wk after the third therapy cycle were used to classify the patients as responders (PSA decline ≥ 50%) or nonresponders (unchanged or increasing PSA level). Quantitative SPECT/CT images were acquired 24, 48, and 168 h after application of 177Lu-PSMA. The absorbed dose for tumor lesions was calculated with dosimetry software. From the pretherapeutic PET/CT scan, the tumor-to-kidney uptake ratio was determined for different SUVs. Results: Regardless of patient response, the kidneys received a mean dose of 0.55 ± 0.20 Gy/GBq per cycle. In the first therapy cycle, the lymph node lesions received a mean dose of 3.73 ± 1.65 Gy/GBq in responders and 1.86 ± 1.25 Gy/GBq in nonresponders (P < 0.01). For bone lesions, the respective mean doses were 3.47 ± 2.00 Gy/GBq and 1.48 ± 0.95 Gy/GBq (P < 0.01). When successive therapy cycles were compared, the mean dose was found to have been reduced from the first to the second cycle by 27% for lymph nodes and by 33% for bone lesions. A significant difference (P < 0.01) in the ratio of lymph node and bone lesion uptake to kidney uptake between responders and nonresponders could be deduced from the pretherapeutic PET/CT scan. Conclusion: Significantly higher doses were achieved for lymph node and bone lesions in responders. The highest absorbed dose, for both lymphatic and osseous lesions, was achieved in the first cycle, decreasing in the second therapy cycle thereafter despite unchanged therapy activities. It may be possible to estimate the response to therapy from the ratio of tumor uptake to kidney uptake obtained from the pretherapeutic PSMA PET/CT scans.

Development of a PROTAC-Based Targeting Strategy Provides a Mechanistically Unique Mode of Anti-Cytomegalovirus Activity.

Human cytomegalovirus (HCMV) is a major pathogenic herpesvirus that is prevalent worldwide and it is associated with a variety of clinical symptoms. Current antiviral therapy options do not fully satisfy the medical needs; thus, improved drug classes and drug-targeting strategies are required. In particular, host-directed antivirals, including pharmaceutical kinase inhibitors, might help improve the drug qualities. Here, we focused on utilizing PROteolysis TArgeting Chimeras (PROTACs), i.e., hetero-bifunctional molecules containing two elements, namely a target-binding molecule and a proteolysis-inducing element. Specifically, a PROTAC that was based on a cyclin-dependent kinase (CDK) inhibitor, i.e., CDK9-directed PROTAC THAL-SNS032, was analyzed and proved to possess strong anti-HCMV AD169-GFP activity, with values of EC50 of 0.030 µM and CC50 of 0.175 µM (SI of 5.8). Comparing the effect of THAL-SNS032 with its non-PROTAC counterpart SNS032, data indicated a 3.7-fold stronger anti-HCMV efficacy. This antiviral activity, as illustrated for further clinically relevant strains of human and murine CMVs, coincided with the mid-nanomolar concentration range necessary for a drug-induced degradation of the primary (CDK9) and secondary targets (CDK1, CDK2, CDK7). In addition, further antiviral activities were demonstrated, such as the inhibition of SARS-CoV-2 replication, whereas other investigated human viruses (i.e., varicella zoster virus, adenovirus type 2, and Zika virus) were found insensitive. Combined, the antiviral quality of this approach is seen in its (i) mechanistic uniqueness; (ii) future options of combinatorial drug treatment; (iii) potential broad-spectrum activity; and (iv) applicability in clinically relevant antiviral models. These novel data are discussed in light of the current achievements of anti-HCMV drug development.

Combinatorial Drug Treatments Reveal Promising Anticytomegaloviral Profiles for Clinically Relevant Pharmaceutical Kinase Inhibitors (PKIs).

Human cytomegalovirus (HCMV) is a human pathogenic herpesvirus associated with a variety of clinical symptoms. Current antiviral therapy is not always effective, so that improved drug classes and drug-targeting strategies are needed. Particularly host-directed antivirals, including pharmaceutical kinase inhibitors (PKIs), may help to overcome problems of drug resistance. Here, we focused on utilizing a selection of clinically relevant PKIs and determined their anticytomegaloviral efficacies. Particularly, PKIs directed to host or viral cyclin-dependent kinases, i.e., abemaciclib, LDC4297 and maribavir, exerted promising profiles against human and murine cytomegaloviruses. The anti-HCMV in vitro activity of the approved anti-cancer drug abemaciclib was confirmed in vivo using our luciferase-based murine cytomegalovirus (MCMV) animal model in immunocompetent mice. To assess drug combinations, we applied the Bliss independence checkerboard and Loewe additivity fixed-dose assays in parallel. Results revealed that (i) both affirmative approaches provided valuable information on anti-CMV drug efficacies and interactions, (ii) the analyzed combinations comprised additive, synergistic or antagonistic drug interactions consistent with the drugs' antiviral mode-of-action, (iii) the selected PKIs, especially LDC4297, showed promising inhibitory profiles, not only against HCMV but also other α-, ß- and γ-herpesviruses, and specifically, (iv) the combination treatment with LDC4297 and maribavir revealed a strong synergism against HCMV, which might open doors towards novel clinical options in the near future. Taken together, this study highlights the potential of therapeutic drug combinations of current developmental/preclinical PKIs.

The trimeric artesunate derivative TF27 exerts strong anti-cytomegaloviral efficacy: Focus on prophylactic efficacy and oral treatment of immunocompetent mice.

Human cytomegalovirus (HCMV) causes serious and even life-threatening diseases, particularly upon congenital or post-transplant infection. Treatment of HCMV infections with currently available drugs targeting viral enzymes is often limited by severe side effects and the emergence of drug-resistant viruses. To avoid this problem, novel therapeutic options directed to host proteins involved in virus replication are being investigated. Recently, we described the pronounced antiherpesviral activity of the trimeric artesunate derivative TF27 at low nanomolar concentrations in vitro and in vivo. In the present study, we report first data on the prophylactic efficacy of TF27 against human and murine CMV and the oncogenic avian alphaherpesvirus Marek's disease virus (MDV). The main findings of this study are (i) a pronounced activity of the experimental drug TF27 against alpha- and betaherpesviruses in vitro upon prophylactic treatment and (ii) a therapeutic and prophylactic efficacy upon oral treatment in an immunocompetent mouse model. Moreover, our data highlight (iii) the tolerability of orally administered TF27 free of compound-associated adverse events and further confirm (iv) the suitability of cellular factors as primary antiviral targets. Thus, we provide evidence for therapeutic and prophylactic antiherpesviral efficacy of TF27 upon oral treatment in immunocompetent hosts and thereby underline its potential for future antiviral drug development.

Artesunate derivative TF27 inhibits replication and pathogenesis of an oncogenic avian alphaherpesvirus.

Nucleoside analogues have been the cornerstone of clinical treatment of herpesvirus infections since the 1970s. However, severe side effects and emergence of drug resistant viruses raise the need for alternative treatment options. We recently investigated the broad and strong antiherpesviral activity of the optimized artesunate derivative TF27 in vitro. TF27 efficiently inhibited replication of the highly oncogenic Marek's disease virus (MDV), a virus that infects chickens, causes deadly lymphomas and threatens poultry populations worldwide. In this study, we used this natural virus-host model for herpesvirus-induced cancer by infecting chickens with MDV, and evaluated the protective efficacy of TF27 and the nucleoside analogue valganciclovir (VGCV) on virus replication and tumorigenesis. We could demonstrate that both drugs reduced viral load in the blood and prevented tumor development in a large portion of the animals. Antiviral treatment also had a positive impact on body weight gain, while no negative compound-associated side effects were observed. This research provides the first evidence that the artesunate derivative TF27 and VGCV can be used in avian species and that they inhibit MDV replication and tumorigenesis. In addition, our study paves the way for promising approaches in future antiherpesviral drug development.

Biodistribution and radiation dosimetry of [18F]-JK-PSMA-7 as a novel prostate-specific membrane antigen-specific ligand for PET/CT imaging of prostate cancer.

AIM: We investigated the whole-body distribution and the radiation dosimetry of [18F]-JK-PSMA-7, a novel 18F-labeled PSMA-ligand for PET/CT imaging of prostate cancer. METHODS: Ten patients with prostate cancer and biochemical recurrence or radiologic evidence of metastatic diseases were examined with 329-384 MBq (mean 359 ± 17 MBq) [18F]-JK-PSMA-7. Eight sequential positron emission tomography (PET) scans were acquired from 20 min to 3 h after injection with IRB approval. The kidneys, liver, lungs, spleen, and salivary glands were segmented into volumes of interest using the QDOSE dosimetry software suite (ABX-CRO, Germany). Absorbed and effective dose were calculated using the ICRP-endorsed IDAC 1.0 package. The absorbed dose of the salivary glands was determined using the spherical model of OLINDA 1.1. PSMA-positive lesions were evaluated separately. Quantitative assessment of the uptake in suspicious lesions was performed by analysis of maximum (max) and peak SUV values. The gluteus maximus muscle (SUVmean) served as a reference region for the calculation of tumor-to-background ratios (TBR's). RESULTS: Physiologic radiotracer accumulation was observed in the salivary and lacrimal glands, liver, spleen, and intestines, in a pattern resembling the distribution known from other PSMA-tracers with excretion via urinary and biliary pathways. The effective dose from [18F]-JK-PSMA-7 for the whole body was calculated to be 1.09E-02 mGy/MBq. The highest radiation dose was observed in the kidneys (1.76E-01 mGy/MBq), followed by liver (7.61E-02 mGy/MBq), salivary glands (4.68E-02 mGy/MBq), spleen (1.89E-02 mGy/MBq), and lungs (1.10E-2 mGy/MBq). No adverse effects of tracer injection were observed. Six out of ten patients were scored as PSMA-positive. A total of 18 suspicious lesions were analyzed, which included six bone lesions, nine lymph nodes, and three local lesions within the prostate fossa. The values for the SUVmax and SUVpeak in the PSMA-positive lesions increased until 60 min p.i. and remained at this intensity in the PET/CT scans until 140 min. In the period between 170 and 200 min after injection, a further significant increase in SUVmax and SUVpeak within the PSMA-positive lesions was observed. CONCLUSIONS: The highest TBR of [18F]-JK-PSMA-7 was found 3 h after injection. From the kinetically collected data, it can be concluded that this trend may also continue in the further course. The start of the PET/CT acquisition should be chosen as late as possible. The high uptake in suspicious lesions in terms of absolute SUVmax and relative TBR values indicates potentially high sensitivity of the tracer for detection of prostate cancer manifestations.

4D-CT-based motion correction of PET images using 3D iterative deconvolution.

OBJECTIVES: Positron emission tomography acquisition takes several minutes representing an image averaged over multiple breathing cycles. Therefore, in areas influenced by respiratory movement, PET-positive lesions occur larger, but less intensive than they actually are, resulting in false quantitative assessment. We developed a motion-correction algorithm based on 4D-CT without the need to adapt PET-acquisition. METHODS: The algorithm is based on a full 3D iterative Richardson-Lucy-Deconvolution using a point-spread-function constructed using the motion information obtained from the 4D-CT. In a motion phantom study (3 different hot spheres in background activity), optimal parameters for the algorithm in terms of number of iterations and start image were estimated. Finally, the correction method was applied to 3 patient data sets. In phantom and patient data sets lesions were delineated and compared between motion corrected and uncorrected images for activity uptake and volume. RESULTS: Phantom studies showed best results for motion correction after 6 deconvolution steps or higher. In phantom studies, lesion volume improved up to 23% for the largest, 43% for the medium and 49% for the smallest sphere due to the correction algorithm. In patient data the correction resulted in a significant reduction of the tumor volume up to 33.3 % and an increase of the maximum and mean uptake of the lesion up to 62.1 and 19.8 % respectively. CONCLUSION: In conclusion, the proposed motion correction method showed good results in phantom data and a promising reduction of detected lesion volume and a consequently increasing activity uptake in three patients with lung lesions.

Thyroid Uptake and Effective Half-Life of Radioiodine in Thyroid Cancer Patients at Radioiodine Therapy and Follow-Up Whole-Body Scintigraphy Either in Hypothyroidism or Under rhTSH.

Adjuvant radioiodine therapy (RITh) for differentiated thyroid carcinoma is performed either with thyroid hormone withdrawal or with administration of recombinant human thyroid-stimulating hormone (rhTSH). Heterogeneous results have been obtained on the impact of the method of patient preparation on thyroid uptake and whole-body effective half-life. A higher radiation exposure using thyroid hormone withdrawal for several weeks compared with rhTSH was reported in prior studies. It was the aim to examine whether these findings are reproducible in a modern protocol with a short interval between surgery and RITh. Methods: A retrospective study was performed on patients admitted for adjuvant RITh for differentiated thyroid carcinoma at the University Hospital of Cologne over a 5-y period from 2010. Dose rate measurements were analyzed for 366 patients, and subgroup analyses were performed for papillary thyroid cancer (n = 341) and follicular thyroid cancer (n = 25) patients, sex, length of hypothyroidism, and normal versus decreased glomerular filtration rate (GFR). Results: The median interval between surgery and RITh was 18 d for thyroid hormone withdrawal and 25 d for rhTSH (P < 0.01). The mean thyroid uptake was 4.2% ± 1.8% for the 300 hypothyroid patients versus 3.8% ± 1.6% (P = 0.12) for the 66 rhTSH patients. Whole-body half-life in the hypothyroid group was significantly longer at 19.3 ± 7.7 h versus 16.4 ± 4.6 h in the rhTSH group (P < 0.01). Results were predominantly influenced by data from the largest subgroup, that is, female papillary thyroid cancer patients. Within this group, whole-body half-life was significantly shorter in the rhTSH treatment arm. Duration of hypothyroidism and a decrease in GFR less than 60 mL/min/1.73 m2 significantly influenced results, with an increased whole-body half-life occurring in the hypothyroid group. When patients returned for whole-body scintigraphy, thyroid, half-life, and whole-body half-life were significantly shorter in the rhTSH groups, resulting in a low thyroid and remaining-body dose. Conclusion: With a shortening of the time between surgery and adjuvant RITh, thyroid uptake is not significantly changed but whole-body half-life becomes longer in the hypothyroid group. Radiation exposure for most patients is not significantly different. However, patients with a hypothyroid phase of more than 4 wk, and in particular those with a decreased GFR, experience higher radiation exposure.

Uptake in non-affected bone tissue does not differ between [18F]-DCFPyL and [68Ga]-HBED-CC PSMA PET/CT.

INTRODUCTION: [68Ga]PSMA-HBED-CC and [18F]DCFPyL show a high potential for the detection of recurrent prostate cancer. While 18F-based tracers have several advantages in availability and image resolution, their sensitivity in the skeleton might be impaired by released [18F]fluoride due to its high bone affinity. In turn, chemically unbound trivalent 68Ga might also accumulate in osseous tissue, in cases of occupied binding sites of plasma proteins and thereby influence bone signal. METHODS: A comparison of average bone SUV was performed in 17 bone-negative and 4 bone-positive patients. All patients underwent PET/CT 125 minutes after application of [18F]DCFPyL and 73 minutes after application of [68Ga]PSMA-HBED-CC at another date. RESULTS: Native SUVs in unaffected bone tissue and SUVs relative to liver uptake were lower in [18F]DCFPyL (0.49) than in [68Ga]PSMA-HBED-CC scans (0.52). SUVs relative to gluteal muscles did not differ between the two tracers. Average lesional SUVs did not differ between tracers. CONCLUSION: No difference of average bone signal intensity was observed for [18F]DCFPyL-PET/CT in comparison to [68Ga]PSMA-HBED-CC scans indicating that diagnostic assessment of the skeleton is not affected by non-specific accumulation of free [18F]fluoride or 68Ga.

Lacrimal Glands May Represent Organs at Risk for Radionuclide Therapy of Prostate Cancer with [(177)Lu]DKFZ-PSMA-617.

PURPOSE: Calculating the absorbed dose is important for the determination of risk and therapeutic benefit of internal radiation therapy. The aim of this study was to perform image-based absorbed dose calculation for critical organs during the first cycle of [(177)Lu]DKFZ-PSMA-617 therapy in a small cohort of patients with metastatic prostate cancer. PROCEDURES: Nine patients with a history of prostate cancer documented by histopathology and radiologic evidence of metastatic diseases underwent radioligand therapy with [(177)Lu]DKFZ-PSMA-617. Conjugated planar whole-body scintigraphies acquired at 0.5, 24, 48, 72, and 168 h post-injection were analyzed by regions of interest, and time-activity curves were generated for various organs. Cumulated activities and residence times were calculated by bi-exponential fit of the time-activity curves. Mean absorbed doses were finally estimated using OLINDA/EXM1.1™. Additionally, the uncertainty when omitting the last measurement (168 h p.i.) was studied. RESULTS: The following mean absorbed doses were calculated: 2.82 mGy/MBq for the lacrimal glands, 0.72 mGy/MBq for the salivary glands, 0.53 mGy/MBq for the kidneys, and 0.42 mGy/MBq for the nasal mucous membrane. Omitting the last measurement resulted in a mean deviation of 10 to 25 % for absorbed dose values as compared to the ones received by analyzing all measurements. CONCLUSION: Absorbed organ doses of [(177)Lu]DKFZ-PSMA-617 therapy are not likely to be critical for kidneys, salivary glands, and the nasal mucous membrane. The lacrimal glands may represent the dose-limiting organs. Whole-body scintigraphy appears sufficient for dose estimation, but late measurements are mandatory, if accurate dose calculation is required.

Radioiodine therapy of benign thyroid disorders: what are the effective thyroidal half-life and uptake of 131I?

AIM: The use of radioiodine therapy is common in the treatment of benign thyroid disease. Council directive Euratom 97/43 requires that for all medical exposure of individuals for radiotherapeutic purposes exposures of target volumes should be individually planned. There are several strategies to accomplish this aim for radioiodine therapy including individual radioiodine uptake measurement and using either individual or mean effective radioiodine uptake and half-life. Although it is always simple to use standard activities, the effective thyroidal half-life and thyroidal uptake of I needs to be estimated individually to achieve optimal dosimetric results. We analyzed the radioiodine half-life and uptake in a large number of patients for use in a semi-individual calculation. METHODS: Patients presenting consecutively between 1 January 2006 and 31 December 2007 were included in the study. Inclusion criteria were the control of hyperthyroidism and withdrawal of antithyroid drugs 2 days before preliminary radioiodine testing and therapy. Patients were treated for Graves' disease (n=363), nontoxic goitre (n=50), toxic goitre (n=639), or toxic uninodular adenoma (n=365). The effective half-life and uptake of I were estimated by uptake measurements after 24 h and 5 days during the preliminary radioiodine test, and serial measurements over 5 days during therapy. RESULTS: The mean effective half-life of I measured during radioiodine therapy was 5.4 days in Graves' disease, 6.4 days in nontoxic goitre, 6.6 days in toxic goitre, and 5.7 days in toxic uninodular adenoma. The mean maximal uptake of I measured during radioiodine therapy was 64% in Graves' disease, 42% in nontoxic goitre, 38% in toxic goitre, and 31% in toxic uninodular adenoma. CONCLUSION: These actual values analyzed here might be used for a semi-individual calculation of therapeutic activity when an individual approach is not possible.

Site-directed sulfhydryl labeling of the oxaloacetate decarboxylase Na+ pump of Klebsiella pneumoniae: helix VIII comprises a portion of the sodium ion channel.

Helix VIII of the beta-subunit of the oxaloacetate decarboxylase of Klebsiella pneumoniae contains the functionally important residues betaN373, betaG377, betaS382, and betaR389. Using a functional oxaloacetate decarboxylase mutant devoid of Cys residues in the beta-subunit, each amino acid residue in helix VIII was replaced individually with Cys. Structural and dynamic features of this region were studied by using site-directed sulfhydryl modification of 20 single-Cys replacement mutants with methanethiosulfonate (MTS) reagents in the absence or presence of Na(+) ions. The pattern of accessibility of the MTS reagents from the periplasmic side of helix VIII shows a periodicity which suggests that this region is alpha-helical. In particular, a water-accessible face comprising betaN373, betaG377, betaS382, betaM386, and betaV390 may be part of a Na(+) channel. Cys residues introduced in the cytoplasmically oriented part of helix VIII were accessible to three different water-soluble MTS compounds and therefore believed to be exposed to water on this side of the membrane. Most residues located in the upper part of helix VIII (residues betaN373-betaV381C) were protected by Na(+) ions for inactivation by the MTS reagents. The distinct results on accessibility toward the different MTS reagents obtained in the presence or absence of Na(+) ions may suggest a conformational change upon binding of Na(+) in this region. The betaR389C mutant had a reduced activity and a pH optimum at pH 9, which could be restored to a wild-type pH optimum of 6.5 and to a 400% gain in activity upon chemical modification with 2-aminoethyl methanethiosulfonate.

Subunit gamma of the oxaloacetate decarboxylase Na(+) pump: interaction with other subunits/domains of the complex and binding site for the Zn(2+) metal ion.

The oxaloacetate decarboxylase Na(+) pump of Klebsiella pneumoniae is an enzyme complex composed of the peripheral alpha subunit and the two integral membrane-bound subunits beta and gamma. The alpha subunit consists of the N-terminal carboxyltransferase domain and the C-terminal biotin domain, which are connected by a flexible proline/alanine-rich linker peptide. To probe interactions between the two domains of the alpha subunit and between alpha-subunit domains and the gamma subunit, the relevant polypeptides were synthesized in Escherichia coli and subjected to copurification studies. The two alpha-subunit domains had no distinct affinity toward each other and could, therefore, not be purified as a unit on avidin-sepharose. The two domains reacted together catalytically, however, performing the carboxyl transfer from oxaloacetate to protein-bound biotin. This reaction was enhanced up to 6-fold in the presence of the Zn(2+)-containing gamma subunit. On the basis of copurification with different tagged proteins, the C-terminal biotin domain but not the N-terminal carboxyltransferase domain of the alpha subunit formed a strong complex with the gamma subunit. Upon the mutation of gamma H78 to alanine, the binding affinity to subunit alpha was lost, indicating that this amino acid may be essential for formation of the oxaloacetate decarboxylase enzyme complex. The binding residues for the Zn(2+) metal ion were identified by site-directed and deletion mutagenesis. In the gamma D62A or gamma H77A mutant, the Zn(2+) content of the decarboxylase decreased to 35% or 10% of the wild-type enzyme, respectively. Less than 5% of the Zn(2+) present in the wild-type enzyme was found if the two C-terminal gamma-subunit residues H82 and P83 were deleted. Corresponding with the reduced Zn(2+) contents in these mutants, the oxaloacetate decarboxylase activities were diminished. These results indicate that aspartate 62, histidine 77, and histidine 82 of the gamma subunit are ligands for the catalytically important Zn(2+) metal ion.