The advent of monoclonal antibody (MAb) technology has made Ehrlich's postulate of the ‘magic bullet’ an attainable goal. Although specific localization of polyvalent antibodies to human gliomas was demonstrated in the 1960s, the lack of specific, high affinity antibody populations and of defined target antigens of sufficient density precluded therapeutic applications. Not until the identification of operationally specific tumor-associated antigens (present in tumor tissue but not normal central nervous system tissue); production of homogeneous, high affinity MAbs to such antigens; and the use of compartmental administration (intrathecal or intracystic), has the promise of passive immunotherapy of primary and metastatic central nervous system neoplasms been recognized. We report here preliminary data from Phase I studies of the compartmental administration of the anti-tenascin MAb 81C6 and F(ab2)2 fragments of MAb Mel-14, which recognizes the proteoglycan chondroitin sulfate-associated protein of gliomas and melanomas, to patients with primary central nervous system tumors or tumors metastatic to the central nervous system. Phase I dose escalation studies of intracystically administered131I-labeled anti-tenascin MAb 81C6 to either spontaneous cysts of recurrent gliomas or surgically created cystic resection cavities have resulted in striking responses. Of five patients with recurrent cystic gliomas treated, four had partial responses, clinically or radiographically. Similarly, in patients with surgically created resection cavities, a partial response at the treatment site and extended stable disease status has been obtained following intracystic administration of131I-labeled 81C6. No evidence of hematologie or neurologic toxicity has been observed in either patient population, with the exception of transient exacerbation of a pre-existing seizure disorder in a single patient. Dosimetry calculations indicated high intracystic retention for four to six weeks with little or no systemic dissemination; estimated total doses intracystically ranged from 12,700–70,290 rad.

Phase I studies of treatment of malignant gliomas and neoplastic meningitis with131I-radiolabeled monoclonal antibodies anti-tenascin 81C6 and anti-chondroitin proteoglycan sulfate Me1-14 F (ab′)2-a preliminary report

We aimed to determine the maximum tolerated dose (MTD) of 131I-labeled 81C6 in patients with leptomeningeal neoplasms or brain tumor resection cavities with subarachnoid communication and to identify any objective responses. 81C6 is a murine IgG monoclonal antibody that reacts with tenascin in gliomas/carcinomas but does not react with normal adult brain. 131I-labeled 81C6 delivers intrathecal (IT) radiation to these neoplasms. This study was a Phase I trial in which patients were treated with a single IT dose of 131I-labeled 81C6. Cohorts of three to six patients were treated with escalating doses of 131I (starting dose, 40 mCi; 20 mCi escalations) on 10 mg 81C6. MTD is defined as the highest dose resulting in serious toxicity in no more than two of six patients. Serious toxicity is defined as grade III/IV nonhematological toxicity or major hematological toxicity. We treated 31 patients (8 pediatric and 23 adult). Eighteen had glioblastoma multiforme. Patients were treated with 131I doses from 40 to 100 mCi. Hematological toxicity was dose limiting and correlated with the administered 131I dose. No grade III/IV nonhematological toxicities were encountered. A partial response occurred in 1 patient and disease stabilization occurred in 13 (42%) of 31 patients. Twelve patients are alive (median follow-up, > 320 days); five are progression free >409 days median posttreatment. The MTD of a single IT administration of 131I-labeled 81C6 in adults is 80 mCi 131I-labeled 81C6. The MTD in pediatric patients was not reached at 131I doses up to 40 mCi normalized for body surface area.

https://clincancerres.aacrjournals.org/content/clincanres/2/6/963.full.pdf

Intrathecal 131I-labeled antitenascin monoclonal antibody 81C6 treatment of patients with leptomeningeal neoplasms or primary brain tumor resection cavities with subarachnoid communication: phase I trial results.

The development of immunotherapeutic protocols for the treatment of human CNS neoplasia over the past two decades has been impressive. Several crucial aspects have been defined, characterized, and in many cases, optimized (Wikstrand CJ, Zalutsky MR, Bigner DD: In: Liau LM, Bigner DD (eds) Brain Tumor Immunotherapy. Humana Press (in press), 2000). Specific Mabs or constructs reacting with targetable antigens are currently available and in clinical trial. In addition, additional antigens currently under study (angiogenesis-related markers, developmentally associated antigens for medulloblastoma such as L1, and the identification of new targets by SAGE, just in its infancy, will provide a veritable library of available targets for therapy. The molecular engineering and affinity maturation techniques being applied to Mab fragment optimization have already been rapidly effective in generating a variety of Mab constructs of appropriate affinity for clinical trial; as new targets are defined, and experience is accrued with the various constructs currently and prospectively available, the optimal targeting of a multitude of antigens will be possible.

Monoclonal antibody therapy of human gliomas: current status and future approaches.

Because of their short range and high linear energy transfer, α-particles may be particularly effective in the treatment of neoplastic meningitis. Monoclonal antibody 81C6 was labeled with α-particle-emitting 211At using N -succinimidyl3-[211At]astatobenzoate, and the efficacy and toxicity of this immunoconjugate were evaluated in an athymic rat model. Animals were given injections via a chronic indwelling catheter with 5 × 105 TE-671 human rhabdomyosarcoma cells and treated 8 days later with single intrathecal doses of either saline or 4–18 µCi of 211At-labeled specific 81C6 antibody or isotype-matched control 211At-labeled 45.6 antibody. In the first experiment, 4, 7, and 13 µCi 211At-labeled 81C6 produced statistically significant ( P = 0.004-0.02) increases in median survival of 33, 29, and 51%, respectively, as compared with saline. Two of 10 animals receiving the 13-µCi dose lived for 6 months before being killed for histological analysis. In the second experiment, 12 µCi of 211At-labeled 45.6 did not increase median survival significantly relative to saline control, while 12 µCi of 211At-labeled 81C6 increased median survival by 113% ( P < 0.005) and resulted in 33% apparent cures. Five of 10 animals receiving 18 µCi of 211At-labeled 81C6 survived until they were killed at 295 days. An additional study was performed in animals given intrathecal injections of 5 × 106 TE-671 cells and given a single dose of 18 µCi of 211At-labeled 81C6 or 211At-labeled 45.6. At this higher cell number, significantly prolonged survival was still seen for specific antibody as compared with saline ( P < 0.001) and control antibody ( P < 0.05). These results suggest that treatment with 211At-labeled monoclonal antibodies may be a valuable approach for neoplastic meningitis.

https://cancerres.aacrjournals.org/content/canres/54/17/4719.full.pdf

Radioimmunotherapy of Neoplastic Meningitis in Rats Using an α-Particle-emitting Immunoconjugate

Background
High-risk and recurrent medulloblastoma (MB) is associated with significant mortality. The murine monoclonal antibody 3F8 targets the cell-surface disialoganglioside GD2 on MB. We tested the efficacy, toxicity, and dosimetry of compartmental radioimmunotherapy (cRIT) with intraventricular 131I-labeled 3F8 in patients with MB on a phase II clinical trial.

Methods
Patients with histopathologically confirmed high-risk or recurrent MB were eligible for cRIT. After determining adequate cerebrospinal fluid (CSF) flow, patients received 2 mCi (where Ci is Curie) 124I-3F8 or 131I-3F8 with nuclear imaging for dosimetry, followed by up to four therapeutic (10 mCi/dose) 131I-3F8 injections. Dosimetry estimates were based on serial CSF and blood samplings over 48 hr plus region-of-interest analyses on serial imaging scans. Disease evaluation included pre- and posttherapy brain/spine magnetic resonance imaging approximately every 3 months for the first year after treatment, and every 6–12 months thereafter.

Results
Forty-three patients received a total of 167 injections; 42 patients were evaluable for outcome. No treatment-related deaths occurred. Toxicities related to drug administration included acute bradycardia with somnolence, headache, fatigue, and CSF pleocytosis consistent with chemical meningitis and dystonic reaction. Total CSF absorbed dose was 1,453 cGy (where Gy is Gray; 350.0–2,784). Median overall survival from first dose of cRIT was 24.9 months (95% confidence interval [CI]:16.3–55.8). Patients treated in radiographic and cytologic remission were at a lower risk of death compared to patients with radiographically measurable disease (hazard ratio: 0.40, 95% CI: 0.18–0.88, P = 0.024).

Conclusions
cRIT with 131I-3F8 is safe, has favorable dosimetry to CSF, and when added to salvage therapy using conventional modalities, may have clinical utility in maintaining remission in high-risk or recurrent MB.

/pdf/a-phase-ii-study-of-radioimmunotherapy-with-intraventricular-48bwzazvam.pdf

A phase II study of radioimmunotherapy with intraventricular 131I-3F8 for medulloblastoma

Ten patients with neoplastic meningitis were treated with a variety of 131I-monoclonal antibody (MAb) conjugates, chosen to bind to their particular malignancy. Pharmacokinetic studies revealed that MAbs leave the ventricular compartment, enter the sub-arachnoid space and then pass into the blood. Once the MAbs enter the blood compartment, their clearance is determined by factors such as circulating anti-mouse Ig and circulating antigens. These lead to complex formations and the clearance of the conjugate by the reticuloendothelial system. In one individual, the anti-mouse Ig response observed systemically was not mirrored within the CSF, which has implications for planning future therapy of this type. In other patients, formation of immune complexes was due to binding to circulating antigen within the blood. The major toxicity associated with the intrathecal administration of 131I-MAbs was bone-marrow suppression. The doses to the bone marrow, resulting from the form of therapy, were calculated but showed no direct correlation with WHO grade 3/4 toxicity. Doses to the ventricular lining were also calculated, but due to the complex geometry of the compartment, calculation of potential tumour doses was not practicable.

Immunoreactivity, pharmacokinetics and bone marrow dosimetry of intrathecal radioimmunoconjugates.

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Immunoreactivity, pharmacokinetics and bone marrow dosimetry of intrathecal radioimmunoconjugates.