Intracavitary radioimmunotherapy of high-grade gliomas: present status and future developments

First clinical experience with fractionated intracavitary radioimmunotherapy using [177Lu]Lu-6A10-Fab fragments in patients with glioblastoma: a pilot study

BACKGROUND

Following resection and standard adjuvant radio- and chemotherapy, approved maintenance therapies for glioblastoma are lacking. Intracavitary radioimmunotherapy (iRIT) with 177Lu-labeled 6A10-Fab fragments targeting tumor-associated carbonic anhydrase XII and injected into the resection cavity offers a novel and promising strategy for improved tumor control.

METHODS

Three glioblastoma patients underwent tumor resection followed by standard radio- and chemotherapy. These patients with stable disease following completion of standard therapy underwent iRIT on compassionate grounds. After surgical implantation of a subcutaneous injection reservoir with a catheter into the resection cavity, a leakage test with [99mTc]Tc-DTPA was performed to rule out leakage into other cerebral compartments. IRIT comprised three consecutive applications over three months for each patient, with 25%, 50%, 25% of the total activity injected. A dosimetry protocol was included with blood sampling and SPECT/CT of the abdomen to calculate doses for the bone marrow and kidneys as potential organs at risk.

RESULTS

All three patients presented without relevant leakage after application of [99mTc]Tc-DTPA. Two patients underwent three full cycles of iRIT (592 MBq and 1228 MBq total activity). One patient showed histologically proven tumor progression after the second cycle (526 MBq total activity). No relevant therapy-associated toxicities or adverse events were observed. Dosimetry did not reveal absorbed doses above upper dose limits for organs at risk.

CONCLUSIONS

In first individual cases, iRIT with [177Lu]Lu-6A10-Fab appears to be feasible and safe, without therapy-related side effects. A confirmatory multicenter phase-I-trial was recently opened and is currently recruiting.

Locoregional Treatment of Glioblastoma With Targeted α Therapy: [ 213 Bi]Bi-DOTA-Substance P Versus [ 225 Ac]Ac-DOTA-Substance P-Analysis of Influence Parameters

BACKGROUND

Glioblastoma (GB) is the most malignant primary brain tumor. Therefore, introduction of new treatment options is critically important. The aim of this study was to assess local treatment with α emitters [ 213 Bi]Bi-DOTA-substance P (SP) and [ 225 Ac]Ac-DOTA-SP.

METHODS

Treatment was performed as salvage therapy in patients with recurrent primary and secondary GB. [ 213 Bi]Bi-DOTA-SP with injected activity 1.85 GBq per cycle was used in 20 primary (48.2 ± 11.8 years old) and in 9 secondary (38.8 ± 10.8 years old) GB patients and [ 225 Ac]Ac-DOTA-SP in 15 primary (45.1 ± 9.9 years old) and in 6 secondary (37.8 ± 6.4 years old) GB patients with a dose escalation scheme (10, 20, and 30 MBq).

RESULTS

Local treatment with [ 213 Bi]Bi-DOTA-SP and [ 225 Ac]Ac-DOTA-SP was well tolerated with only few adverse effects. There was no statistically significant difference between [ 213 Bi]Bi-DOTA-SP and [ 225 Ac]Ac-DOTA-SP groups in survival parameters. For primary GB, survival parameters of patients treated with [ 213 Bi]Bi-DOTA-SP and [ 225 Ac]Ac-DOTA-SP were as follows(in months): progression-free survival time, 2.7 versus 2.4; OS-d (overall survival from time of diagnosis to death from any cause), 23.6 versus 21.0; OS-t (overall survival from the start of treatment to death from any cause), 7.5 versus 5.0; and OS-r (overall survival from recurrence in primary tumors to death from any cause), 10.9 versus 12.0. Survival parameters of secondary GB patients treated with [ 213 Bi]Bi-DOTA-SP and [ 225 Ac]Ac-DOTA-SP were as follows (in months): progression-free survival time, 5.8 versus 2.4; OS-d, 52.3 versus 65.0; OS-t, 16.4 versus 16.0; and OS-c (overall survival from conversion into secondary GB multiforme to death from any cause), 18.4 versus 36.0.

CONCLUSIONS

The similarity results of 213 Bi or 225 Ac may suggest that the local treatment of brain tumors can be greatly simplified. The experience to date shows that local radioisotope treatment of brain tumors requires further dosimetry studies, taking into account the complexity of biological processes.

Elastin-like Polypeptide Hydrogels for Tunable, Sustained Local Chemotherapy in Malignant Glioma

Glioblastoma (GBM) is a primary brain tumor that carries a dismal prognosis, which is primarily attributed to tumor recurrence after surgery and resistance to chemotherapy. Since the tumor recurrence appears near the site of surgical resection, a concept of immediate and local application of chemotherapeutic after initial tumor removal could lead to improved treatment outcome. With the ultimate goal of developing a locally-applied, injectable drug delivery vehicle for GBM treatment, we created elastin-like polypeptide (ELP) hydrogels. The ELP hydrogels can be engineered to release anti-cancer drugs over an extended period. The purpose of this study was to evaluate the biomechanical properties of ELP hydrogels, to characterize their ability to release doxorubicin over time, and to investigate, in vitro, the anti-proliferative effect of Dox-laden ELP hydrogels on GBM. Here, we present microstructural differences, swelling ratio measurements, drug release characteristics, and in vitro effects of different ELP hydrogel compositions. We found that manipulation of the ELP–collagen ratio allows for tunable drug release, that the released drug is taken up by cells, and that incubation with a small volume of ELP-Dox hydrogel drastically reduced survival and proliferation of GBM cells in vitro. These results underscore the potential of ELP hydrogels as a local delivery strategy to improve prognosis for GBM patients after tumor resection.

Novel NK1R-Targeted 68Ga-/177Lu-Radioconjugates with Potential Application against Glioblastoma Multiforme: Preliminary Exploration of Structure-Activity Relationships

Locoregionally administered, NK1 receptor (NK1R) targeted radionuclide therapy is a promising strategy for the treatment of glioblastoma multiforme. So far, the radiopharmaceuticals used in this approach have been based on the endogenous agonist of NK1R, Substance P or on its close analogues. Herein, we used a well-known, small molecular NK1R antagonist, L732,138, as the basis for the radiopharmaceutical vector. First, 14 analogues of this compound were evaluated to check whether extending the parent structure with linkers of different lengths would not deteriorate the NK1R binding. The tested analogues had affinity similar to or better than the parent compound, and none of the linkers had a negative impact on the binding. Next, five DOTA conjugates were synthesized and used for labelling with ⁶⁸Ga and ¹⁷⁷Lu. The obtained radioconjugates turned out to be fairly lipophilic but showed rather limited stability in human plasma. Evaluation of the receptor affinity of the (radio)conjugates showed that neither the chelator nor the metal negatively impacts the NK1R binding. The ¹⁷⁷Lu-radioconjugates exhibited the binding characteristics towards NK1R similar or better than that of the ¹⁷⁷Lu-labelled derivative of Substance P, which is in current clinical use. The experimental results presented herein, along with their structural rationalization provided by modelling, give insight for the further molecular design of small molecular NK1R-targeting vectors.

Imaging and treatment of brain tumors through molecular targeting: Recent clinical advances

Molecular imaging techniques have rapidly progressed over recent decades providing unprecedented in vivo characterization of metabolic pathways and molecular biomarkers. Many of these new techniques have been successfully applied in the field of neuro-oncological imaging to probe tumor biology. Targeting specific signaling or metabolic pathways could help to address several unmet clinical needs that hamper the management of patients with brain tumors. This review aims to provide an overview of the recent advances in brain tumor imaging using molecular targeting with positron emission tomography and magnetic resonance imaging, as well as the role in patient management and possible therapeutic implications.

Efficacy of nimotuzumab (hR3) conjugated with 131I or 90Y in laryngeal carcinoma xenograft mouse model

PURPOSE

The humanized monoclonal antibody hR3, both alone and in combination with other chemotherapeutic agents and radiotherapy, can be used to treat head and neck cancers. Substantial progress has been made in the development of targeted radioimmunotherapy using iodine-131 (131I) and yttrium-90 (90Y) radioisotopes in recent years. In the present study, we examined the efficacy of hR3 conjugated with 131I or 90Y to inhibit tumor growth in a laryngeal carcinoma xenograft tumor model.

METHODS

hR3 was labeled with 131I or 90Y to generate the conjugates 131I-hR3 or 90Y-hR3. The conjugates were incubated with HEp-2 laryngeal carcinoma cells to evaluate binding capacity. The efficacy of the labeled hR3 conjugates to treat laryngeal cancer was also evaluated in nude mice inoculated with HEp-2 tumors.

RESULTS

The purified radioimmunoconjugates with specific activities of 187-191 MBq/mg had radiochemical purity >98% and >80% immunoreactivity with HEp-2 cells. Mice with HEp-2 xenografts treated with 131I-hR3 or 90Y-hR3 showed reduced tumor volume and improved survival rates compared to the untreated control group and the group treated with unlabeled hR3. At equivalent doses, radioimmunotherapeutic hR3 labeled with 90Y had increased tumor inhibition activity compared to hR3 labeled with 131I.

CONCLUSIONS

131I-hR3 and 90Y-hR3 are promising targeted radiopharmaceuticals for treatment of head and neck cancers, especially laryngeal cancers.

Historical Perspective on Surgery and Survival with Glioblastoma: How Far Have We Come?

BACKGROUND

Glioblastoma multiforme remains a therapeutic challenge. We offer a historical review of the outcomes of patients with glioblastoma from the earliest report of surgery for this lesion through the introduction of modern chemotherapeutics and aggressive approaches to tumor resection.

METHODS

We reviewed all major surgical series of patients with glioblastoma from the introduction of craniotomy for glioma (1884) to 2020.

RESULTS

The earliest reported craniotomy for glioblastoma resulted in the patient's death less than a month after surgery. Improved intracranial pressure management resulted in improved outcomes, reducing early postoperative mortality from 50% to 6% in Harvey Cushing's series. In the first major surgical series (1912), the mean survival was 10.1 months. This figure did not improve until the introduction of radiotherapy in the 1950s, which doubled survival relative to those who had surgery alone. The most recent significant advance, chemotherapy with the alkylating agent temozolomide, extended survival by 2.5 months compared with surgery and radiotherapy alone (14.6 and 12.1 months, respectively). This protocol remains the standard regimen for newly diagnosed glioblastoma. The innovative treatments being investigated have yet to show a survival benefit.

CONCLUSIONS

With advancements in localization, imaging, anesthesia, surgical technique, control of cerebral edema, and adjuvant therapies, outcomes in glioblastoma improved incrementally from Cushing's time until the introduction of magnetic resonance imaging enabled better degrees of resection in the 1990s. Modest improvements came with the advent of biomarker-driven targeted chemotherapy in the first decade of the current century.