Clinical Internal Dosimetry and Biodistribution of 177 Lu-DOTA-Trastuzumab in HER2-Positive Metastatic and Locally Advanced Breast Carcinoma

OBJECTIVE

The aim of this study was to assess the biodistribution and dosimetry of 177 Lu-DOTA-trastuzumab in patients with HER2-positive breast carcinoma using whole-body (WB) planar imaging at multiple time points.

PATIENTS AND METHODS

This study was a prospective evaluation of HER2-positive metastatic/locally advanced breast carcinoma patients who underwent gamma camera imaging for dosimetry and biodistribution studies by using 177 Lu-DOTA-trastuzumab. The standard diagnostic dosimetry protocol was followed, which included cold trastuzumab injection followed by in-house produced 177 Lu-DOTA-trastuzumab. Serial WB planar images (anterior and posterior) were obtained on gamma camera after the infusion of 177 Lu-DOTA-trastuzumab at multiple time points. Whole-body and organ regions of interest were drawn, and the numbers of disintegrations were obtained. The mean absorbed doses for the liver, spleen, kidneys, heart, red marrow, and tumor were obtained from OLINDA EXM v2.1.1 and ORIGIN software.

RESULTS

The study included a cohort of 21 female breast carcinoma patients. Tracer activity ( 177 Lu-DOTA-trastuzumab) was noted in the physiological organs such as the liver, spleen, kidneys, heart, as well as in the tumors. On visual analysis of 177 Lu-DOTA-trastuzumab biodistribution, the liver activity showed gradual clearance over time, and although spleen was comparatively faintly visualized than liver and similarly, kidneys were faintly visualized suggestive of the alternate route of tracer excretion. The maximum number of patients (n = 12) showed 2 components of clearance, namely, fast and slow. The average effective half-life of all the patients (including single and 2 components of clearance) was 106.25 ± 22.14 hours (84.11-128.39 hours). The mean absorbed dose for the liver, spleen, kidneys, heart, whole body, and red marrow was 1.0702 ± 0.731, 1.4114 ± 0.462, 1.4232 ± 0.364, 1.4719 ± 0.602, 0.2412 ± 0.0295, and 0.1485 ± 0.0213 mGy/MBq, respectively, by OLINDA EXM and 0.5741 ± 0.333, 0.8096 ± 0.224, 0.7943 ± 0.235, 1.8971 ± 0.713, and 0.09619 ± 0.0144 for liver, spleen, kidneys, heart and whole body respectively by ORIGIN. The absorbed radiation dose for tumor was 1.94E+2 by OLINDA EXM software and 1.78E+2 by ORIGIN software. In this study, during and after infusion of 177 Lu-DOTA-trastuzumab, no major adverse effects were noted in any patient except 1 patient who had grade 1 nausea and managed conservatively by antiemetic drug.

CONCLUSIONS

The results of our study demonstrated expected and favorable biodistribution and dosimetry with 177 Lu-DOTA-trastuzumab in HER2-positive breast carcinoma patients. We noticed the mean absorbed dose to the normal organs within the limits of maximum tolerable dose, and also tumor dose was higher than the normal liver dose. Therefore, we conclude that 177 Lu-DOTA-trastuzumab radioimmunotherapy is feasible and a safe treatment option for treating HER2-positive breast carcinoma patients.

Intricacies in the Preparation of Patient Doses of [177Lu]Lu-Rituximab and [177Lu]Lu-Trastuzumab Using Low Specific Activity [177Lu]LuCl3: Methodological Aspects

The development of humanized monoclonal antibodies (MAbs) with Lutetium-177 ([177Lu]Lu3+) has brought a paradigm shift in the arena of targeted therapy of various cancers. [177Lu]Lu-DOTA-Rituximab and [177Lu]Lu-DOTA-Trastuzumab have gained prominence due to their improved therapeutic efficacy in the treatment of lymphoma and breast cancer. The clinical dose formulation of these radiolabeled MAbs, using low specific activity [177Lu]LuCl3, requires extensive optimization of the radiolabeling protocol. The present study merits the development of a single protocol which has been optimized for conjugation of Rituximab and Trastuzumab with p-NCS-benzyl-DOTA and further radiolabeling these immunoconjugates (ICs) with low specific activity [177Lu]LuCl3. Herein, we report a consistent and reproducible protocol for clinical dose formulations of [177Lu]Lu-DOTA-Rituximab and [177Lu]Lu-DOTA-Trastuzumab (~9.25 GBq each, equivalent to ~2 patient doses) with radiochemical yield (RCY) between 84 and 86% and radiochemical purities (RCP) >99%. The in vitro stabilities of both these radioimmunoconjugates (RICs) were retained up to 120 h post-radiolabeling, upon storage with L-ascorbic acid as stabilizer (concentration: ~ 220-240 μg/37MBq) at -20 °C. The ready-to-use formulation of clinical doses[177Lu]Lu-DOTA-Rituximab and [177Lu]Lu-DOTA-Trastuzumab has been successfully achieved by employing a single optimized protocol. While [177Lu]Lu-DOTA-Rituximab has exhibited a high degree of localization in retroperitoneal nodal mass of refractory lymphoma patient, high uptake of [177Lu]Lu-DOTA-Trastuzumab has been observed in metastatic breast carcinoma patient with multiple skeletal metastases.

A method to prevail false positive responses due to excess cations and viscous nature of Radiopharmaceuticals in Limulus Amebocyte Lysate Gel Clot test

OBJECTIVES

Bacterial endotoxin test (BET) for detection and quantification of endotoxin in radiopharmaceuticals (RPs), used for therapy or diagnosis, is prerequisite to administration in patients. Out of the two established methods used for this purpose (Kinetic Chromogenic Assay: KCM and Gel Clot Bacterial Endotoxin Test: GC-BET), GC-BET is recommended by pharmacopeias to evaluate the interferences exhibited during the assay due to presence of various ingredients in samples. In the present study, the influence of excess of cations in [¹⁷⁷Lu]Lu-DOTATATE, used for Peptide Receptor Radionuclide Therapy (PRRT), were studied and a protocol to negate the enhancement observed was developed. Additionally, a protocol for carrying out GC-BET for extremely viscous [¹³¹I]I-Lipiodol was standardized.

METHODS

GC-BET was performed for [¹⁷⁷Lu]Lu-DOTATATE and [¹³¹I]I-Lipiodol at maximum valid dilution (MVD), using LRW as a diluent. To negate the false positivity observed in case of [¹⁷⁷Lu]Lu-DOTATATE, various concentrations of calcium chloride (CaCl₂) were added and evaluated for the reversal of the interference observed initially. To prevail the difficulty in performing GC-BET for [¹³¹I]I-Lipiodol various modification in the protocols like orbital vortexing at different rpm and time intervals were performed. KCM assays were also performed for studied RPs at MVD.

RESULTS

It was observed that at MVD, [¹⁷⁷Lu]Lu-DOTATATE exhibited false positivity in GC-BET. However, all the individual reagents used in labeling of [¹⁷⁷Lu]Lu-DOTATATE did not show any false positivity. Finally, performing the assay with an addition of 2mM CaCl₂ (final concentration) nullified the false positivity. Further, intricacy in performing GC-BET for [¹³¹I]I-Lipiodol due to its viscosity was resolved by orbital vortexing at 3000 rpm for 5 minutes.

CONCLUSIONS

Our study proved that false positivity was observed in GC-BET for [¹⁷⁷Lu]Lu-DOTATATE due to the presence excess M³⁺ ions. Further, our study is the first of its kind which demonstrated methods for negating these false positive results by using modified protocol and hypothesizing the reason behind the enhancement. Additionally, ours is the first study which proved that a simple step of vortexing the viscous RPs like [¹³¹I]I-Lipiodol can resolved the problems encountered during performing GC-BET due to viscosity of RPs.

Therapeutic Multidose Preparation of a Ready-to-Use 177Lu-PSMA-617 Using Carrier Added Lutetium-177 in a Hospital Radiopharmacy and Its Clinical Efficacy

Introduction: [¹⁷⁷Lu]Lu-prostate-specific membrane antigen (PSMA)-617 has emerged as a promising radiopharmaceutical for targeting PSMA in metastatic castrate-resistant prostate carcinoma (mCRPC). We have optimized the radiolabeling protocol for a multidose formulation (27-28.8 GBq equivalent to 6-7 patient-doses) of [¹⁷⁷Lu]Lu-PSMA-617 using [¹⁷⁷Lu]Lu³⁺ produced via ¹⁷⁶Lu(n,γ)¹⁷⁷Lu route with moderate specific activity (0.66-0.81 GBq/μg). Methods: [¹⁷⁷Lu]Lu-PSMA-617 was synthesized using moderate specific activity [¹⁷⁷Lu]LuCl₃ (0.74 GBq/μg) with PSMA-617 having metal-to-ligand molar ratio ∼1: 2.5 in CH₃COONH₄ buffer (0.1 M) containing gentisic acid at pH 4.0-4.5. Human prostate carcinoma cell line LNCaP cell (high PSMA expression) was used for in vitro cell-binding studies and generating tumor xenograft models in nude mice for tissue biodistribution studies. Several batches of the present formulation have been clinically administered in mCRPC patients (single patient dose: 4.44-5.55 GBq per cycle). Results: In this study we report a consistent and reproducible protocol for multidose formulations of [¹⁷⁷Lu]Lu-PSMA-617 for adopting in a hospital radiopharmacy setting. Although the radiochemical yield of [¹⁷⁷Lu]Lu-PSMA-617 was found to be 97.30% ± 1.03%, the radiochemical purity was 98.24% ± 0.50% (n = 19). In vitro and serum stability of [¹⁷⁷Lu]Lu-PSMA-617 was retained up to 72 and 120 h after radiolabeling and upon storage at -20°C with a radioactive concentration between 0.37 and 0.74 GBq/mL upon using stabilizer concentration as low as 43-48 μg/mCi. Preclinical cell-binding studies of [¹⁷⁷Lu]Lu-PSMA-617 revealed specific binding with LNCaP cells of 17.4% ± 2.4%. The uptake in LnCaP xenografted tumor (nude mice) was 7.5 ± 2.6% ID/g for ∼1.5-2.0 cm³ tumor volume at 24-h post-injection. Post-therapy (24 h) SPECT image of mCRPC patients with prior orchidectomy and various hormone therapy showed specific localization of [¹⁷⁷Lu]Lu-PSMA-617 in the tumor region. Conclusions: Formulation of a ready-to-use multidose formulation of [¹⁷⁷Lu]Lu-PSMA-617 was successfully achieved and the procedure was optimized for routine preparation at a hospital radiopharmacy set-up. High degree of localization of [¹⁷⁷Lu]Lu-PSMA-617 in post-therapy SPECT scan and the post-therapeutic response confirms its therapeutic efficacy. Clinical Trials.gov ID: RPC/51/Minutes/Final dated 16th October, 2019.

Clinical Efficacy of Sodium [99mTc] Pertechnetate from Low Specific Activity 99Mo/99mTc Autosolex Generator in Hospital Radiopharmacy Centre

BACKGROUND

Few nuclear reactors in the world producing high specific activity (HSA) 99Mo using enriched 235U (HEU), are aging and are planned for shut down in the near future. Further, HEU will not be freely available, due to safeguards, and the technology for 99Mo from low-enriched 235U (LEU) is not yet widely accepted since 239Pu contamination in the product is an issue. Production of 99mTc from low specific activity (LSA) 99Mo obtained from 98Mo(n,)99Mo reaction in research reactor and 100Mo(,n)99Mo reaction in accelerator or directly from 100Mo(p,2n)99mTc nuclear reaction in cyclotron, has been explored [1]. The methyl ethyl ketone (MEK) based solvent extraction technique is n well known method for the separation of 99mTc from low specific activity 99Mo. The 99Mo/99mTc autosolex generator [2], a computer controlled automated module, utilizes the conventional MEK solvent extraction method for extraction of 99mTc. Herein, we have validated the usage of autosolex for preparation of pharmacopoeia grade 99mTcO4- from 7.40-27.5 GBq of LSA 99Mo-SodiumMolybdate (99MoO42-) solution and validated the quality of the 99mTcO4- by preparing wide range of 99mTc-radiopharmaceuticals (99mTc-RP).

MATERIALS AND METHODS

The 99mTcO4- was extracted from the autosolex as described in [2] starting from 7.40-27.5 GBq of LSA 99MoO42- and subjected to the required physico-chemical and biological quality control (QC) tests. The eluted 99mTcO4- labeled various fourth generation 99mTc radiopharmaceuticals cold kits (99mTc-cold kits) apart from regular 99mTc-cold kits in our centre. Various 99mTc-RP extracted 99mTcO4- using standard procedures [3] were prepared and subjected to required QC as Indian Pharmacopeia monograph [4] and used in scintigraphic imaging in patients. The radiation exposure dose to the operator were compared between autosolex and manual MEK based solvent extraction generator.

RESULTS

The extracted 99mTcO4- from autosolex is a clear and colorless solution with pH between 5.0-6.5. The elemental molybdenum (Mo) and aluminum (Al) content <10µg/mL, MEK levels <0.1%, 99Mo breakthrough <0.030% and radiochemical purity (RCP) >98%. All the extracted 99mTcO4- batches complies sterility test, endotoxin limit (EL) <5EU/mL. The RCP of all the labeled 99mTc-RP >95%. The autosolex delivers much less radiation dose to the operator than the convention manually handled MEK based solvent extraction generator.

CONCLUSIONS

Autosolex Generator was successfully used to obtain pharmaceutical grade 99mTcO4- from LSA 99MoO42- and generator is safe in radiological and pharmacological point of view. The suitability of the autosolex for use in hospital radiopharmacy was shown by using the 99mTcO4- to prepare various 99mTc-RP and using these 99mTc-RP for scintigraphic imaging in patients.

On the Separation of Yttrium-90 from High-Level Liquid Waste: Purification to Clinical-Grade Radiochemical Precursor, Clinical Translation in Formulation of 90Y-DOTATATE Patient Dose

Introduction: The quality control parameters of in-house-produced ⁹⁰Y-Acetate from high-level liquid waste (HLLW) using supported liquid membrane (SLM) technology were validated and compared with the pharmacopeia standard. The radiolabeling of DOTATATE yielding ⁹⁰Y-DOTATATE in acceptable radiochemical purity (RCP), with expected pharmacological behavior in in vivo models, establish the quality of ⁹⁰Y-Acetate. Clinical translation of ⁹⁰Y-Acetate in formulation of ⁹⁰Y-DOTATATE adds support toward its use as clinical-grade radiochemical. Methods: Quality control parameters of ⁹⁰Y-Acetate, namely radionuclide purity (RNP), were evaluated using β^- spectrometry, γ-spectroscopy, and liquid scintillation counting. RCP and metallic impurities were established using high-performance liquid chromatography and inductively coupled plasma optical emission spectrometry, respectively. The suitability of ⁹⁰Y-Acetate as an active pharmaceutical ingredient radiochemical was ascertained by radiolabeling with DOTATATE. In vivo biodistribution of ⁹⁰Y-DOTATATE was carried out in nude mice bearing AR42J xenografted tumor. Clinical efficacy of ⁹⁰Y-DOTATATE was established after using in patients with large-volume neuroendocrine tumors (NET). Bremsstrahlung imaging was carried out in dual-head gamma camera with a wide energy window setting (100-250 keV). Results: In-house-produced ⁹⁰Y-Acetate was clear, colorless, and radioactive concentration (RAC) in the range of 40-50 mCi/mL. RCP was >98%. ⁹⁰Sr content was <0.85 μCi/Ci of ⁹⁰Y. Gross λ content was <0.8 nCi/Ci of ⁹⁰Y and no γ peak was observed. Fe³⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ contents were <1.7 μg/Ci. The radiolabeling yield (RLY) of ⁹⁰Y-DOTATATE was >94%, RCP was >98%. The in vitro stability of ⁹⁰Y-DOTATATE was up to 72 h postradiolabeling, upon storage at -20°C. Post-therapy (24 h) Bremsstrahlung image of patients with large NET exhibit complete localization of ⁹⁰Y-DOTATATE in tumor region. Conclusions: This study demonstrates that the in-house-produced ⁹⁰Y-Acetate from HLLW can be used for the formulation of various therapeutic ⁹⁰Y-based radiopharmaceuticals. Since ⁹⁰Y is an imported radiochemical precursor available at a high cost in India, this study which demonstrates the suitability of indigenously sourced ⁹⁰Y, ideally exemplifies the recovery of "wealth from waste." The Clinical Trial Registration number: (P17/FEB/2019).

Underestimation of malignancy in biopsy-proven cases of stromal fibrosis

OBJECTIVE

To determine the rate of underestimation of malignancy in patients with biopsy-proven stromal fibrosis.

METHODS

Following institutional review board approval, we retrospectively reviewed the charts of patients with biopsy-proven stromal fibrosis who underwent percutaneous breast biopsy in the 5-year period between 1 January 2005 and 31 December 2009. The medical records and the histopathology in patients who underwent repeat biopsy and/or surgical excision at the site of stromal fibrosis within 2 years were reviewed. Interval stability for up to 2 years was documented in patients who did not undergo additional biopsy or surgical excision. An upgrade was defined as any patient with biopsy-proven stromal fibrosis or fibroadenoma with evidence of malignancy at the site of biopsy within 2 years.

RESULTS

365 cases of stromal fibrosis were identified, of which 25 (7%) were upgraded to in situ or invasive malignancy on repeat biopsy or surgical excision. 7 were upgraded to ductal carcinoma in situ and 18 were upgraded to invasive cancer. Of the upgraded cases, 8 out of 24 (32%) were considered concordant with a benign diagnosis. The false-negative rate, that is, cases of stromal fibrosis concordant with benignity, but with subsequent upgrade, comprised 2% of all cases.

CONCLUSION

In biopsy-proven cases of stromal fibrosis, there is a 7% upgrade to malignancy. We recommend that all instances of stromal fibrosis with radiology-pathology discordance undergo repeat biopsy or surgical excision. Cases that demonstrate radiology-pathology concordance can be safely categorized as a Breast Imaging Reporting and Data System 3 (BI-RADS® 3) lesion with a 6-month follow-up, owing to a false-negative rate for missed cancer of 2%.

ADVANCES IN KNOWLEDGE

We now recommend that concordant cases of stromal fibrosis be categorized as BI-RADS 3 with a short-term follow-up, as this results in a missed cancer rate of 2%.

Relative potential for selection of quinolone-resistance-determining-region mutations in Streptococcus pneumoniae by gemifloxacin, gatifloxacin and moxifloxacin

Serial passage of a clinical isolate of Streptococcus pneumoniae, in the presence of moxifloxacin, gatifloxacin or gemifloxacin, gave rise to resistant isolates. Non-susceptibility as defined by Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS) breakpoints arose on Days 10, 11, and 12 with gatifloxacin, gemifloxacin, and moxifloxacin respectively. Moxifloxacin and gatifloxacin selected for a single step quinolone-resistant-determining-region (QRDR) mutation in DNA gyrase (GyrA) on Day 4 and 7 respectively, whereas gemifloxacin selected simultaneously for multi-step mutations in gyrase and topoisomerase IV (ParC) on Day 17 and activated a non-reserpine inhibited efflux mechanism by Day 4. As found in clinical isolates, mutations included Ser-81-Phe and Glu-85-Lys in GyrA and Ser-79-Phe or Asp-83-Tyr in ParC. At high MICs, moxifloxacin showed a previously unreported 4 amino-acid deletion in GyrB as well as a more unusual substitution Ser-79-Leu/Ile in ParC. Gemifloxacin showed a 2- to 16-fold greater activity than moxifloxacin or gatifloxacin against strains with two or more QRDR mutations, however, its potency did not translate to nonsusceptibility and gemifloxacin MIC values were either at or well above the CLSI nonsusceptible breakpoint concentration.