Prototyping Trastuzumab Docetaxel Immunoliposomes with a New FCM-Based Method to Quantify Optimal Antibody Density on Nanoparticles

Developing targeted nanoparticles is a rising strategy to improve drug delivery in oncology. Antibodies are the most commonly used targeting agents. However, determination of their optimal number at the surface remains a challenging issue, mainly due to the difficulties in measuring precisely surface coating levels when prototyping nanoparticles. We developed an original quantitative assay to measure the exact number of coated antibodies per nanoparticle. Using flow cytometry optimized for submicron particle analysis and beads covered with known amounts of human IgG-kappa mimicking various amounts of antibodies, this new method was tested as part of the prototyping of docetaxel liposomes coated with trastuzumab against Her2+ breast cancer. This quantification method allowed to discriminate various batches of immunoliposomes depending on their trastuzumab density on nanoparticle surface (i.e., 330 (Immunoliposome-1), 480 (Immunoliposome-2) and 690 (Immunoliposome-3), p = 0.004, One-way ANOVA). Here we showed that optimal number of grafted antibodies on nanoparticles should be finely tuned and highest density of targeting agent is not necessarily associated with highest efficacy. Overall, this new method should help to better prototype third generation nanoparticles.

CHK1 inhibition in soft-tissue sarcomas: biological and clinical implications

Background

Inhibition of ChK1 appears as a promising strategy for selectively potentiate the efficacy of chemotherapeutic agents in G1 checkpoint-defective tumor cells such as those that lack functional p53 protein. The p53 pathway is commonly dysregulated in soft-tissue sarcomas (STS) through mutations affecting TP53 or MDM2 amplification. GDC-0575 is a selective ATP-competitive inhibitor of CHK1.

Methods

We have performed a systematic screening of a panel of 10 STS cell lines by combining the treatment of GDC-0575 with chemotherapy. Cell proliferation, cell death and cell cycle analysis were evaluated with high throughput assay. In vivo experiments were carried out by using TP53-mutated and TP53 wild-type patient-derived xenograft models of STS. Clinical activity of GDC-0575 combined with chemotherapy in patients with TP53-mutated and TP53 wild-type STS was also assessed.

Results

We found that GDC-0575 abrogated DNA damage-induced S and G2-M checkpoints, exacerbated DNA double-strand breaks and induced apoptosis in STS cells. Moreover, we observed a synergistic or additive effect of GDC-0575 together with gemcitabine in vitro and in vivo in TP53-proficient but not TP53-deficient sarcoma models. In a phase I study of GDC-0575 in combination with gemcitabine, two patients with metastatic TP53-mutated STS had an exceptional, long-lasting response despite administration of a very low dose of gemcitabine whereas one patient with wild-type TP53 STS had no clinical benefit. Genetic profiling of samples from a patient displaying secondary resistance after 1 year showed loss of one preexisting loss-of-function mutation in the helical domain of DNA2.

Conclusion

We provide the first preclinical and clinical evidence that potentiation of chemotherapy activity with a CHK1 inhibitor is a promising strategy in TP53-deficient STS and deserves further investigation in the phase II setting.

Abstract P5-01-03: HER2 imaging by SPECT-CT using 111In radiolabeled pertuzumab-fab DOTAGA-conjugate: A proof of concept study in a preclinical model of breast cancer

Introduction: HER2 is positive in approximately 20-30% of all breast cancer and is associated with poor prognosis, higher mortality and higher metastatic incidence. Current diagnosis of HER2 expression relies on invasive methods requiring tissue biopsy which can lead to variable results due to inter/intra-metastatic and intratumoral heterogeneity in breast cancers. It has been recently demonstrated that HER2 molecular imaging based on pertuzumab, an antibody targeting HER2, could represent a more accurate non-invasive method to assess HER2 expression and evaluate its spatial and temporal heterogeneity. Aim: In the present study, we aimed at developing radiolabeled pertuzumab Fab fragments for HER2 imaging. Tumor uptake of radiolabeled Fab was evaluated in an animal model of HER2 breast cancer by SPECT-CT, and the impact of trastuzumab on HER2 imaging was assessed. The objective of this study was to validate the feasibility of HER2 imaging with a pertuzumab-derived probe and to evaluate the possible translation of such a probe for clinical use in patients treated or not with anti-HER2 therapy. Methods: Fab fragments of pertuzumab have been generated by papain digestion and bioconjugated with the bifunctional chelating agent DOTAGA for incorporation of Indium 111 to generate an HER2-specific probe for SPECT (111In-DOTAGA-pertuzumab-Fab). The functionality of both radiolabeled Fab and whole pertuzumab was evaluated by in vitro assays using HER2-overexpressing human breast cancer cell line (HCC1954). Tumor uptake of pertuzumab-Fab and whole pertuzumab (111In-DOTAGA-Pertuzumab) has been evaluated in Balb/c nude mice bearing BT-474 tumors with or without pre-treatment with trastuzumab for 24h. Results: In the current study we demonstrate that Fab fragments of pertuzumab keep similar HER2 binding properties than whole pertuzumab and can therefore be a suitable HER2-targeted probe. In vivo, 111In-DOTAGA-pertuzumab-Fab showed better pharmacokinetics than whole pertuzumab with faster tumor uptake and blood clearance allowing faster imaging with better tumor/blood ratio. In addition, tumor uptake of 111In-DOTAGA-pertuzumab-Fab is not modified by pre-treatment with trastuzumab. Conclusion: We assume that radiolabeled pertuzumab-Fab should be of great interest if the intention to treat is based on anti-HER2 monoclonal antibodies-based therapies rather than small molecules (e.g. lapatinib). Interestingly, pertuzumab has been shown to be also beneficial in combination with trastuzumab and chemotherapy in non-metastatic patients through its approval for the neoadjuvant treatment and very recently in the APHINITY clinical trial aiming for an approval in the adjuvant treatment of early breast cancer. These data suggest that pertuzumab will be extensively used in various HER-2 positive breast cancers underlining the interest to perform molecular imaging of HER2 expression as a predictive biomarker of efficacy.

Citation Format: Oudot A, Bellaye P-S, Vrigneaud J-M, Raguin O, Bernhard C, Dumont L, Brunotte F, Savina A, Bouquet F, Fumoleau P, Collin B. HER2 imaging by SPECT-CT using 111In radiolabeled pertuzumab-fab DOTAGA-conjugate: A proof of concept study in a preclinical model of breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-01-03.

Autologous dendritic cells prolong allograft survival through Tmem176b-dependent antigen cross-presentation

The administration of autologous (recipient-derived) tolerogenic dendritic cells (ATDCs) is under clinical evaluation. However, the molecular mechanisms by which these cells prolong graft survival in a donor-specific manner is unknown. Here, we tested mouse ATDCs for their therapeutic potential in a skin transplantation model. ATDC injection in combination with anti-CD3 treatment induced the accumulation of CD8(+) CD11c(+) T cells and significantly prolonged allograft survival. TMEM176B is an intracellular protein expressed in ATDCs and initially identified in allograft tolerance. We show that Tmem176b(-/-) ATDCs completely failed to trigger both phenomena but recovered their effect when loaded with donor peptides before injection. These results strongly suggested that ATDCs require TMEM176B to cross-present antigens in a tolerogenic fashion. In agreement with this, Tmem176b(-/-) ATDCs specifically failed to cross-present male antigens or ovalbumin to CD8(+) T cells. Finally, we observed that a Tmem176b-dependent cation current controls phagosomal pH, a critical parameter in cross-presentation. Thus, ATDCs require TMEM176B to cross-present donor antigens to induce donor-specific CD8(+) CD11c(+) T cells with regulatory properties and prolong graft survival.

[A rare case of hypokalemic thyrotoxic periodic paralysis in a Caucasian patient with Basedow's disease]

Thyrotoxicosis periodic paralysis is a very rare complication of thyrotoxicosis in whites, but is more frequently reported in oriental and latin american populations and associates the clinical picture of hyperthyroidism with bouts of paralysis due to hypokalemia. The hypokalemia is due to a massive shift of potassium from the extra- to the intracellular compartment. In this paper the authors report a case of 34-years old white male with an history of hypokalemic periodic paralysis and hyperthyroidism, studied with potassium, thyroid hormone, TSH and thyroid antibodies sampling and thyroid ultrasonography with color-Doppler. The restoration of a euthyroid state with methimazole and propranolol was effective in preventing further episodes of paralysis. It is suggested that the mechanism for the development of the hypokalemic periodic paralysis is the intracellular blockade of potassium by the surplus of thyroid hormones.

[The MRI sites functioning in 1987 in France. Results of a survey]

A study of the 23 MRI sites functioning in France at the end of 1987 provides an overall view of the organizational and economic aspects of these sites as well as an initial assessment of their activity in terms of the types of equipment used and the institutions, private or public, within which they have been set up.

[Interest of the dosage of serum ferritin in hemodialyzed patients (author's transl)]

The ferrous stock evaluation can be done to-day in a repetitive manner through the serum ferritin radio-assay. In 33 hemodialyzed patients, the ferrous lack is frequent and was found with a rate of 62%. It is profound in four cases and concealed in 17 cases. The serum ferritin has no correlation with the ordinary hematologic and biologic parameters. Its value stays in the Ag HBs positive patient. The oral ferrous treatment to the patient with a low ferritin rate (less than 30 ng/ml) induces a ferritin and a hemoglobin rate increased, so confirming the therapeutic efficacy when done with a rational prescription.

[Space of initial distribution of transferrin labeled with indium 113m (author's transl)]

The over-estimate of plasma volume noted at the time of the substitution of iodine 131 labeled human serum albumin by indium 113m transferrin, probably results from a defective fastening of the radionucleide on the binding protein and not at all from a particular behavior of this last one as it has often been admitted.

[Estimate of coronary blood flow by simple fixation measurement of 86Rb on the cardiac muscle (author's transl)]

The method for measuring coronary blood flow, which is described here, is based on the estimate, by external detection, of the quantity of 86Rb fastened on the cardiac muscle about ten minutes after the injection. The discussion which follows after this report, shows that the use of such a late time for the measurements does not contradict the fondamental hypothesis but allows to work in perfect technical conditions. The results obtained,widely superposable to those which have been published until to-day, prove a posteriori the availability of the method.

[Error introduced in the radiocardiographic measurement of right volume by the non linearity of the detector in high count rates (author's transl)]

The short life tracers permit the use of high activities and so allow to follow with a good statistic accuracy fast phenomenons such as the different phases of cardiac revolution. However, this advantage may be quickly limited by the dead-time of the detection unit used. It results from this, in high activities, a non linear response which introduces non negligible errors which we have calculated and verifies thanks to experience in the measurement of right ventricular volumes.

[Evaluation of the parietal factor interfering in the measurement of cardiac output by external detection with the aid of 99mTc labelled red cells (author's transl)]

The results of a radioisotopic exploration are not independant of the physical characteristics of the tracer used. Thus in the measurement of cardiac output index by external detection, the substitution of 131I fastened on the human serum albumine by 99mTc fastened on red cells introduces a systematic average error of +20% whose origin is double. Because of the plasma or red cell kind of the tracer, the average error done on the volume is, in 130 measurements, 26% whereas that which results from the difference of photon energy is -6%. Only this last error affects the measurement of the cardiac output and, by that time, it is demonstrated that a direct determination of the cardiac output index by STEWART-HAMILTON'S relation is impossible.