Phase 0 Radiopharmaceutical-Agent Clinical Development

Leveraging Programmatic Collaboration for a Radiopharmaceutical Clinic

Radiation oncologists, radiopharmacists, nuclear medicine physicians, and medical oncologists have seen a renewed clinical interest in radiopharmaceuticals for the curative or the palliative treatment of cancer. To allow for the discovery and the clinical advancement of targeted radiopharmaceuticals, these stakeholders have reformed their trial efforts and remodeled their facilities to accommodate the obligations of a program centered upon radioactive investigational drug products. Now considered informally as drugs and not beam radiotherapy, radiopharmaceuticals can be more easily studied in the traditional clinical trial enterprise ranging from phase 0-I to phase III studies. Resources and physical facilities allocated to radiopharmaceuticals have brought forth new logistics and patient experience for safe and satisfactory drug delivery. The clinical use of theranostic agents-that is, diagnostic and therapeutic radionuclide pairs-has accelerated radiopharmaceutical development.

Human gastrin- releasing peptide receptor expression in women with uterine cervix cancer

Introduction

²¹²Pb-DOTAM-GRPR1 is a pharmaceutical radioimmunoconjugate consisiting of an α-particle-emitting radionuclide lead-212 (²¹²Pb), a metal chelator DOTAM (1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane), and a gastrin-releasing peptide receptor (GRPR)-targeted antagonist currently being evaluated as therapy in uterine cervix and other cancer types. Previous studies have revealed that a variable proportion of uterine cervix cancer tumors overexpress the radiopharmaceutical target GRPR when assessed by cell proportion and staining intensity immunoreactive scores (IRS). Tumor response to ²¹²Pb-DOTAM-GRPR1 strongly associates with GRPR overexpression, and therefore, it seems reasonable to assess uterine cervix cancer GRPR immunoreactivity for greater insight into the feasibility of using ²¹²Pb-DOTAM-GRPR1 as a radiopharmaceutical treatment.

Methods

We examined a series of 33 uterine cervix cancer paraffin-embedded tumors in order to establish whether this tumor type overexpresses GRPR at an IRS score of 6 or higher, as ²¹²Pb-DOTAM-GRPR1 is currently being evaluated in clinical trials against tumors showing such a level of expression.

Results

The results show that five of five (100%) primary adenocarcinomas and 10 of 16 (63%) primary squamous cell tumors overexpress GRPR at an IRS score of 6 or higher.

Discussion

The frequency of overexpression in this study suggests that ²¹²Pb-DOTAM-GRPR1 radiopharmaceutical treatment may be useful in the management of persistent, recurrent, or metastatic uterine cervix cancer patients. A phase I clinical trial involving patients with metastatic uterine cervix cancer is currently underway (NCT05283330).

Human epidermal growth factor receptor 2 expression in women with uterine cervix adenocarcinoma from Appalachian Kentucky

Introduction

High-risk human epidermal growth factor receptor 2 (HER2)-positive adenocarcinomas associate with early recurrence and death, prompting consideration of novel radiotherapeutic options like a trastuzumab-linked thorium-227 alpha-particle emitting radionuclide.

Methods

We conducted a retrospective pilot biomarker study of uterine cervix cancers among patients in Appalachian Kentucky, to characterize an exploitable triage biomarker like HER2 expression before starting a prospective phase 0 trial.

Results

Most (60%) adenocarcinomas showed HER2 cell-surface overexpression, whereas squamous cell carcinomas (4%) did not do so.

Discussion

Further validation tests of HER2 expression as a triage biomarker for radiopharmaceutical selection are warranted.

A Primer on Radiopharmaceutical Therapy

The goal of this article is to serve as a primer for the United States-based radiation oncologist who may be interested in learning more about radiopharmaceutical therapy (RPT). Specifically, we define RPT, review the data behind its current and anticipated indications, and discuss important regulatory considerations for incorporating it into clinical practice. RPT represents an opportunity for radiation oncologists to leverage 2 key areas of expertise, namely therapeutic radiation therapy and oncology, and apply them in a distinct context in collaboration with nuclear medicine and medical oncology colleagues. Although not every radiation oncologist will incorporate RPT into their day-to-day practice, it is important to understand the role for this modality and how it can be appropriately used in select patients.

Radiopharmaceutical Validation for Clinical Use

Radiopharmaceuticals are reemerging as attractive anticancer agents, but there are no universally adopted guidelines or standardized procedures for evaluating agent validity before early-phase trial implementation. To validate a radiopharmaceutical, it is desirous for the radiopharmaceutical to be specific, selective, and deliverable against tumors of a given, molecularly defined cancer for which it is intended to treat. In this article, we discuss four levels of evidence—target antigen immunohistochemistry, in vitro and in vivo preclinical experiments, animal biodistribution and dosimetry studies, and first-in-human microdose biodistribution studies—that might be used to justify oncology therapeutic radiopharmaceuticals in a drug-development sequence involving early-phase trials. We discuss common practices for validating radiopharmaceuticals for clinical use, everyday pitfalls, and commonplace operationalizing steps for radiopharmaceutical early-phase trials. We anticipate in the near-term that radiopharmaceutical trials will become a larger proportion of the National Cancer Institute Cancer Therapy Evaluation Program (CTEP) portfolio.

Radiopharmaceutical Switch Maintenance for Relapsed Ovarian Carcinoma

Switch maintenance, or using alternative therapeutic agents that were not administered during a prior course of cancer treatment, has emerged as an active clinical research and regulatory agency-approvable path in the National Cancer Institute (NCI) Cancer Therapy Evaluation Program (CTEP) drug-development sequence. To better inform the design of therapeutic radiopharmaceutical trials, we reviewed academic scholarship discussing the clinical use of maintenance approaches to cancer treatment. Women with advanced-stage primary platinum-refractory or platinum-resistant ovarian carcinoma and their courses of treatment provide context for our discussion. Twenty-four (10%) out of 244 trials for women with ovarian carcinoma fit our search terms for maintenance trials. Five (2%) trials studied radiopharmaceuticals as switch maintenance. In our opinion, radiopharmaceutical switch maintenance merits further testing in prospective trials for women with advanced-stage primary platinum recurrent or refractory ovarian carcinoma.