Site-specific 68Ga-labeled nanobody for PET imaging of CD70 expression in preclinical tumor models

BACKGROUND

CD70-CD27 is a costimulatory ligand-receptor pair in the tumor necrosis factor receptor family. With only limited expression in normal tissues, CD70 is constitutively expressed in a variety of solid tumors and hematologic malignancies, facilitating immunosuppression through CD27 signaling in the tumor microenvironment by enhanced survival of regulatory T cells, induction of T cell apoptosis, and T cell exhaustion. Consequently, CD70 is an increasingly recognized target for developing antibody-based therapies, but its expression patterns vary among different tumor types in spatial distribution, magnitude of expression and percentage of positive cells. In that regard, individual confirmation of CD70 expression at screening and during treatment could enhance the successful implementation of anti-CD70 therapies. Here, we developed a gallium-68 (⁶⁸Ga) radiolabeled single-domain antibody-fragment targeting CD70 for in vivo positron emission tomography (PET) imaging.

RESULTS

An anti-CD70 VHH construct containing a C-direct-tag with a free thiol was developed to enable site-specific conjugation to a NOTA bifunctional chelator for ⁶⁸Ga radiolabeling. [⁶⁸Ga]Ga-NOTA-anti-CD70 VHH was obtained in good radiochemical yield of 30.4 ± 1.7% and high radiochemical purity (> 94%). The radiolabeled VHH showed excellent in vitro and in vivo stability. Specific binding of [⁶⁸Ga]Ga-NOTA-anti-CD70 VHH was observed on CD70^high 786-O cells, showing significantly higher cell-associated activity when compared to the blocking condition (p < 0.0001) and CD70^low NCl-H1975 cells (p < 0.0001). PET imaging showed specific radiotracer accumulation in CD70 expressing human tumor xenografts, which was efficiently blocked by prior injection of unlabeled anti-CD70 VHH (p = 0.0029). In addition, radiotracer uptake in CD70^high tumors was significantly higher when compared with CD70^low tumors (p < 0.0001). The distribution of the radioactivity in the tumors using autoradiography was spatially matched with immunohistochemistry analysis of CD70 expression.

CONCLUSION

[⁶⁸Ga]Ga-NOTA-anti-CD70 VHH showed excellent in vivo targeting of CD70 in human cancer xenografts. PET imaging using this radioimmunoconjugate holds promise as a non-invasive method to identify and longitudinally follow-up patients who will benefit most from anti-CD70 therapies.

Complement inhibition prevents glial nodal membrane injury in a GM1 antibody-mediated mouse model

The involvement of the complement pathway in Guillain-Barré syndrome pathogenesis has been demonstrated in both patient biosamples and animal models. One proposed mechanism is that anti-ganglioside antibodies mediate neural membrane injury through the activation of complement and the formation of membrane attack complex pores, thereby allowing the uncontrolled influx of ions, including calcium, intracellularly. Calcium influx activates the calcium-dependent protease calpain, leading to the cleavage of neural cytoskeletal and transmembrane proteins and contributing to subsequent functional failure. Complement inhibition has been demonstrated to provide effective protection from injury in anti-ganglioside antibody-mediated mouse models of axonal variants of Guillain-Barré syndrome; however, the role of complement in the pathogenesis of demyelinating variants has yet to be established. Thus, it is currently unknown whether complement inhibition would be an effective therapeutic for Guillain-Barré syndrome patients with injuries to the Schwann cell membrane. To address this, we recently developed a mouse model whereby the Schwann cell membrane was selectively targeted with an anti-GM1 antibody resulting in significant disruption to the axo-glial junction and cytoplasmic paranodal loops, presenting as conduction block. Herein, we utilize this Schwann cell nodal membrane injury model to determine the relevance of inhibiting complement activation. We addressed the early complement component C2 as the therapeutic target within the complement cascade by using the anti-C2 humanized monoclonal antibody, ARGX-117. This anti-C2 antibody blocks the formation of C3 convertase, specifically inhibiting the classical and lectin complement pathways and preventing the production of downstream harmful anaphylatoxins (C3a and C5a) and membrane attack complexes. Here, we demonstrate that C2 inhibition significantly attenuates injury to paranodal proteins at the node of Ranvier and improves respiratory function in ex vivo and in vivo Schwann cell nodal membrane injury models. In parallel studies, C2 inhibition also protects axonal integrity in our well-established model of acute motor axonal neuropathy mediated by both mouse and human anti-GM1 antibodies. These data demonstrate that complement inhibition prevents injury in a Schwann cell nodal membrane injury model, which is representative of neuropathies associated with anti-GM1 antibodies, including Guillain-Barré syndrome and multifocal motor neuropathy. This outcome suggests that both the motor axonal and demyelinating variants of Guillain-Barré syndrome should be included in future complement inhibition clinical trials.

Cusatuzumab for treatment of CD70-positive relapsed or refractory cutaneous T-cell lymphoma

BACKGROUND

The clinical benefit of cusatuzumab, a CD70-directed monoclonal antibody with enhanced effector functions, was investigated in patients with relapsed/refractory (R/R) cutaneous T-cell lymphoma (CTCL).

METHODS

In this cohort expansion of the ARGX-110-1201 study, 27 patients with R/R CTCL received cusatuzumab at 1 (n = 11) or 5 mg/kg (n = 16) once every 3 weeks to investigate its safety, dose, and exploratory efficacy. The pharmacokinetics, immunogenicity, CD70 expression, and CD70/CD27 biology were also assessed.

RESULTS

The most common adverse events included infusion-related reactions, pyrexia, and asthenia. Eighteen serious adverse events (grade 1-3) were reported in 11 patients; 1 of these (vasculitis) was considered drug-related. For 8 of the 11 patients receiving 1 mg/kg, anti-drug antibodies (ADAs) affected the minimal concentration, and this resulted in undetectable cusatuzumab concentrations at the end of treatment and, in some cases, a loss of response. This effect was greatly reduced in the patients receiving 5 mg/kg. The overall response rate was 23%; this included 1 complete response and 5 partial responses (PRs) in 26 of the 27 evaluable patients. In addition, 9 patients achieved stable disease. The mean duration on cusatuzumab was 5.2 months, and the median duration was 2.5 months. Patients with Sézary syndrome (SS) achieved a 60% PR rate with a dosage of 5 mg/kg and a 33% PR rate with a dosage of 1 mg/kg; this resulted in an overall response rate of 50% for patients with SS at both doses.

CONCLUSIONS

Cusatuzumab was well tolerated, and antitumor activity was observed at both 1 and 5 mg/kg in highly pretreated patients with R/R CTCL. The observed dose-dependent effect on exposure supports the use of 5 mg/kg for future development.

An open-label, nonrandomized, phase Ib feasibility study of cusatuzumab in patients with nasopharyngeal carcinoma

CD70 is expressed in up to 80% of nasopharyngeal carcinoma (NPC) cases. Cusatuzumab is a humanized anti‐CD70 monoclonal antibody, with dual action mechanisms: induction of cytotoxicity against CD70⁺ tumor cells and reduction in CD70‐CD27 signaling mediated immune evasion. The aim of this study was to assess the safety, pharmacokinetic profile, immunogenicity, pharmacodynamic profile, and preliminary activity of cusatuzumab in advanced NPC. Eleven patients were enrolled: one patient was assigned to arm A (adjuvant cusatuzumab monotherapy after curative chemoradiation), nine patients to arm B (cusatuzumab monotherapy; noncurative setting), and one patient to arm C (cusatuzumab + chemotherapy; noncurative setting); irrespective of tumoral CD70 expression. Both patients in arms A and C completed the study. All patients in arm B discontinued at an early stage. Five patients experienced grade greater than or equal to 3 nondrug related treatment‐emergent adverse events, most commonly fatigue and pneumonia (18%). An infusion‐related reaction was observed in two of 11 patients. Laboratory results showed no trend over time. Seven patients were eligible for response evaluation. No objective response to cusatuzumab was observed with stable disease being the best response. The current study indicates that the safety profile of cusatuzumab (with or without concurrent chemotherapy) is manageable in patients with advanced NPC, which is consistent with known safety profile. Limited activity of cusatuzumab in advanced NPC was observed. Combination therapies of cusatuzumab and other types of therapy should be explored for the improvement of activity in NPC and other CD70‐expressing malignancies.

Precise methane absorption measurements in the 1.64 μm spectral region for the MERLIN mission

In this article we describe a high-precision laboratory measurement targeting the R(6) manifold of the 2ν₃ band of ¹²CH₄. Accurate physical models of this absorption spectrum will be required by the Franco-German, Methane Remote Sensing LIDAR (MERLIN) space mission for retrievals of atmospheric methane. The analysis uses the Hartmann-Tran profile for modeling line shape and also includes line-mixing effects. To this end, six high-resolution and high signal-to-noise absorption spectra of air-broadened methane were recorded using a frequency-stabilized cavity ring-down spectroscopy apparatus. Sample conditions corresponded to room temperature and spanned total sample pressures of 40 hPa - 1013 hPa with methane molar fractions between 1 μmol mol^-1 and 12 μmol mol^-1. All spectroscopic model parameters were simultaneously adjusted in a multispectrum nonlinear least-squares fit to the six measured spectra. Comparison of the fitted model to the measured spectra reveals the ability to calculate the room-temperature, methane absorption coefficient to better than 0.1% at the on-line position of the MERLIN mission. This is the first time that such fidelity has been reached in modeling methane absorption in the investigated spectral region, fulfilling the accuracy requirements of the MERLIN mission. We also found excellent agreement when comparing the present results with measurements obtained over different pressure conditions and using other laboratory techniques. Finally, we also evaluated the impact of these new spectral parameters on atmospheric transmissions spectra calculations.

Multiscale structural characterizations of mixed U(iv)–An(iii) oxalates (An(iii) = Pu or Am) combining XAS and XRD measurements

Thorough XRD and XAS measurements confirmed the existence of M_2.2UIV1.8AnIII0.2(C₂O₄)₅·nH₂O (An = Pu or Am) oxalate solid solutions.

Constraints on WIMP dark matter from the high energy PAMELA p/p data

A new calculation of the p[over ]/p ratio in cosmic rays is compared to the recent PAMELA data. The good match up to 100 GeV allows us to set constraints on exotic contributions from thermal weakly interacting massive particle (WIMP) dark matter candidates. We derive stringent limits on possible enhancements of the WIMP p flux: a mWIMP=100 GeV (1 TeV) signal cannot be increased by more than a factor of 6 (40) without overrunning PAMELA data. Annihilation through the W+W- channel is also inspected and cross-checked with e+/(e-+e+) data. This scenario is strongly disfavored as it fails to simultaneously reproduce positron and antiproton measurements.

Uterine artery pseudo-aneurysm: diagnosis and therapy during pregnancy

Arterial aneurysms and pseudo-aneurysms are a rare but recognized cause of obstetric hemorrhage. Diagnosis during pregnancy, prior to rupture, is exceptional. We report the first case of diagnosis and treatment of an uterine artery pseudo-aneurysm during pregnancy.