Is it possible that there is a connection between an individual’s gut microbiota and the ability to fight off gastrointestinal (GI) cancer? Findings from a preliminary research study performed by researchers in South Korea suggest that a link between the two may exist and that fecal microbiota transplants (FMTs) may enhance the efficacy of immunotherapies for GI cancer patients.
The proof-of-concept clinical trial, conducted at the Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea, analyzed how an FMT could help 13 patients with metastatic solid tumors that were resistant to the anti-PD-1 antibody drug known as nivolumab (Opdivo). Anti-PD-1 drugs are immunotherapies that help treat cancer by improving an individual’s immune response against cancer cells.
Four of the trial participants had gastric cancer, five had esophageal cancer, and the remaining four had hepatocellular carcinoma. The patients were given a colonoscopy to implant the FMTs. The recipients also received antibiotics to reduce the response of their existing microbiotas.
The FMT donors also had gastric cancer, esophageal cancer, or hepatocellular carcinoma. Prior to donating their fecal matter, the donors experienced complete or partial response to the anti-PD-1 drugs nivolumab or pembrolizumab (Keytruda) for at least six months after receiving initial treatments.
“This research highlights the complex interplay between beneficial and detrimental bacteria within the gut microbiota in determining treatment outcomes,” co-senior study author Hansoo Park, MD, PhD, Assistant Professor, Biomedical Science and Engineering, Gwangju Institute of Science and Technology, told The ASCO Post. “While the connection between gut microbiota and immune response to cancer therapy has been a growing area of interest, our study provides concrete evidence and new avenues for improving treatment outcomes in a broader range of cancers,” he added. Further studies may confirm the need for microbiome testing by clinical laboratories to guide clinicians treating patients with colon cancers. (Photo copyright: Gwangju Institute of Science and Technology.)
Surprising Results
Fecal material for an FMT procedure combines donated fecal matter with a sterile saline solution which is then filtered to produce a liquid solution. That solution is then administered to the recipient via colonoscopy, upper GI endoscopy, enema, or an oral capsule. The solution may also be frozen for later use.
Upon analyzing the recipients, the scientists found that six of the patients (46.2%) who had experienced resistance to immunotherapies for their cancers, benefitted from the FMTs.
“Both donors were long-lasting, good responders to anti-PD-1 inhibitors, but because we did not yet know the causative bacteria responsible for the [FMT] response, we could not predict whether the treatment would be effective,” she added.
The researchers also determined that the presence of a bacterial strain known as Prevotella merdae helped to improve the effectiveness of the FMTs, while two strains of bacteria—Lactobacillus salivarius and Bacteroides plebeius (aka, Phocaeicola plebeius)—had a detrimental impact on the transplants.
Challenges to Widespread Adoption of FMTs
The researchers acknowledge there are challenges in widespread acceptance and use of FMTs in treating cancers but remain optimistic about the possibilities.
“Developing efficient and cost-effective methods for production and distribution is necessary for widespread adoption,” Sook Ryun Park told The ASCO Post. “Addressing these challenges through comprehensive research and careful planning will be essential for integrating FMT into the standard of care for cancer treatment.”
More research and clinical trials are needed before this use of FMTs can be utilized in clinical settings. However, the study does demonstrate that the potential benefits of FMTs may improve outcomes in patients with certain cancers. As this happens, microbiologists may gain a new role in analyzing the microbiomes of patients with gastrointestinal cancers.
“By examining the complex interactions within the microbiome, we hope to identify optimal microbial communities that can be used to enhance cancer treatment outcomes,” Hansoo Park told The ASCO Post. “This comprehensive approach will help us understand how the microbial ecosystem as a whole contributes to therapeutic success.”
FDA is streamlining how new diagnostic tests are approved; encourages IVD companies to focus on ‘qualifying biomarkers’ in development of new cancer drugs
It is good news for the anatomic pathology profession that new insights into the human immune system are triggering not only a wave of new therapeutic drugs, but also the need for companion diagnostic tests that help physicians decide when it is appropriate to prescribe immunotherapy drugs.
Rapid advances in precision medicine, and the discovery that a patient’s own immune system can be used to suppress chronic disease, have motivated pharmaceutical companies to pursue new research into creating targeted therapies for cancer patients. These therapies are based on a patient’s physiological condition at the time of diagnosis. This is the very definition of precision medicine and it is changing how oncologists, anatomic pathologists, and medical laboratories diagnose and treat cancer and other chronic diseases.
Since immunotherapy drugs require companion diagnostic tests, in vitro diagnostic (IVD) developers and clinical laboratory and pathology group leaders understand the stake they have in pharma companies devoting more research to developing these types of drugs.
New cancer drugs combined with targeted therapies would directly impact the future of anatomic pathology and medical laboratory testing.
Targeted Therapies Cost Less, Work Better
Targeted therapies focus on the mechanisms driving the cancer, rather than on destroying the cancer itself. They are designed to treat cancers that have specific genetic signatures.
One such example of a targeted therapy is pembrolizumab (brand name: Keytruda), a humanized antibody that targets the programmed cell death 1 (PD-1) receptor. The injection drug was primarily designed to treat melanoma. However, the FDA recently expanded its approval of Keytruda to include treatment of tumors with certain genetic qualities, regardless of the tumor’s location in the body. It was the first time the FDA has expanded an existing approval.
In a Forbes article, David Shaywitz, MD, PhD, noted that pembrolizumab had “an unprecedented type of FDA approval … authorizing its use in a wide range of cancers.” Shaywitz is Chief Medical Officer of DNAnexus in Mountain View, Calif.; Visiting Scientist, Department of Biomedical Informatics at Harvard Medical School; and Adjunct Scholar, American Enterprise Institute.
Cancers with high mutational burdens respond to the therapy because they are more likely to have what Shaywitz calls “recognizable novel antigens called mutation-associated neoantigens, or MANAs.” Such cancers include melanomas, non-small cell lung cancer, some rare forms of colorectal cancers, and others.
Such therapies require genetic sequencing, and because sequencing is becoming faster and less expensive—as is the analysis of the sequencing—the information necessary to develop targeted therapies is becoming more accessible, which is part of what’s motivating pharma research.
Biomarkers and Traditional versus Modern Drug Testing and Development
At the same time pharma is developing new immunotherapies, the FDA is recognizing the benefit of faster approvals. In an FDA Voice blog post, Janet Woodcock, MD, Director of the Center for Drug Evaluation and Research (CDER) at the FDA, wrote, “In the past three years alone, [we have] approved more than 25 new drugs that benefit patients with specific genetic characteristics … and we have approved many more new uses—also based on specific genetic characteristics—for drugs already on the market.”
In his Forbes article, Shaywitz notes that pembrolizumab’s development foreshadows a “More general trend in the industry,” where the traditional phases of drug testing and development in oncology are becoming less clear and distinct.
Along with the changes to drug development and approval that precision medicine is bringing about, there are also likely to be changes in how cancer patients are tested. For one thing, biomarkers are critical for precision medicine.
However, pharmaceutical companies have not always favored using biomarkers. According to Shaywitz, “In general, commercial teams tend not to favor biomarkers and seek to avoid them wherever possible.” And that, “All things being equal, a doctor would prefer to prescribe a drug immediately, without waiting for a test to be ordered and the results received and interpreted.”
In July, just weeks after expanding its approval for Keytruda, the FDA approved a Thermo Fisher Scientific test called the Oncomine Dx Target Test. A Wired article describes it as “the first next-generation-sequencing-based test” and notes that it “takes a tiny amount of tumor tissue and reports on alterations to 23 different genes.”
Thermo Fisher’s Oncomine DX Target Test (above) is the first multi-drug next-generation sequencing test approved by the FDA. The test is a companion diagnostic for lung-cancer drugs made by Novartis and Pfizer. (Caption and photo copyright: Thermo Fisher Scientific.)
Unlike pembrolizumab, however, the Oncomine Dx Target Test did not enjoy fast-track approval. As Wired reported, “Getting the FDA’s approval took nearly two years and 220,000 pages of data,” in large part because it was the first test to include multiple genes and multiple drugs. Thus, according to Joydeep Goswami, PhD, President of Clinical Next Generation Sequencing at Thermo Fisher, “That put the technology under extraordinary scrutiny.”
FDA Encouraging Use of Biomarkers in Precision Medicine Therapies
The FDA, however, is taking steps to make that process easier. Woodcock noted in her FDA Voice blog post that the agency is actively encouraging drug developers to “use strategies based on biomarkers.” She added that the FDA currently “works with stakeholders and scientific consortia in qualifying biomarkers that can be used in the development of many drugs.”
Additionally, in a column he penned for Wired, Robert M. Califf, MD, former Commissioner of the FDA, states that the organization has “begun to lay out a flexible roadmap for regulatory approval.” He notes, “Given the complexity of NGS [next-generation-sequencing] technology, test developers need assurance as well, and we’ve tried to reduce uncertainty in the process.”
Regulations that assist IVD developers create viable diagnostics, while ensuring the tests are accurate and valid, will be nearly as important in the age of precision medicine as the therapies themselves.
All of these developmental and regulatory changes will impact the work done by pathologists and medical laboratories. And since precision medicine means finding the right drug for the individual patient, then monitoring its progress, all of the necessary tests will be conducted by clinical laboratories.
Faster approvals for these new drugs and tests will likely mean steep learning curves for pathologists. But if the streamlined regulation process being considered by the FDA works, new immunoassay tests and targeted therapies could mean improved outcomes for cancer patients.
