Proteomics, Metabolomics Could Stratify Women at Risk for Common, But Serious Pregnancy Conditions

Noninvasive prenatal testing (NIPT) for trisomies has dominated the obstetrics-related diagnostic headlines and masked the lack of development for diagnostics for other pregnancy-related conditions. While rapid adoption of NIPT is improving clinical obstetric care, clinicians see a desperate need for diagnostics development in the underserved areas of common, but adverse, conditions of pregnancy like preterm birth and preeclampsia.

"NIPT has been driven by technological advancements. Next-generation sequencing has made it easier to get access to genetic information," Robin Tuytten, Ph.D., vice president research and development at Metabolomic Diagnostics (Ireland) tells DTET. "We can get our heads around it because screening for chromosomal aberrations builds off of existing tests in the market place."

Louise Kenny, M.B.Ch.B., Ph.D., from Cork University Maternity Hospital in Ireland says that there has been nearly no new development of obstetrics screening tests, besides NIPT, in nearly 30 years. She acknowledges conditions like preeclampsia and preterm birth are complex syndromes, but have been neglected in terms of research and development by both public and private entities.

Preterm Birth
Experts say that costs associated with preterm birth are on average more than $54,000, or ten times higher than the cost of a baby delivered at full term. Preterm birth is common, with the U.S. Centers for Disease Control and Prevention saying that one of every 10 births is affected. Preterm birth is tied to neonatal and early childhood morbidity as well as increased risk of major long-term medical complications, including learning disabilities, cerebral palsy, and vision and hearing loss.

Frustratingly to care providers, the majority of preterm births are spontaneous and not tied to known prenatal or maternal medical conditions. Prior history of spontaneous preterm delivery and cervical length measurements are considered the best measures of clinical risk to date, but individually or in combination, they fail to predict the majority of spontaneous preterm deliveries. Researchers are hopeful that emerging diagnostics will soon be able to identify women at higher risk of preterm birth through biomarkers early in pregnancy, before symptoms appear.

"The intrauterine space is both physically and ethically remote. As such, this is perhaps why, with the possible exception of the measurement of cervical length by ultrasound, little recent progress has been made in the development of useful biomarkers to stratify patients according to risk of SPTB," writes David Cantonwine, Ph.D., from Brigham and Women's Hospital in Boston, Mass., in a study published Feb. 10 in the American Journal of Obstetrics & Gynecology (AJOG). "The evolving field of circulating microparticle biology may offer a solution to these difficulties as these particles present a sampling of the utero-placental environment. Additionally, studying the contents of these particles holds the promise of identifying novel blood-based, and possibly clinically useful, biomarkers."

In the AJOG study, the researchers found functional proteomic factors, known to be associated with biological processes that already had distinguishable expression profiles at 10 to 12 weeks gestational age among women who go on to deliver spontaneously at 34 weeks or less. The researchers analyzed plasma specimens obtained between 10 and 12 weeks gestation as part of a prospective birth cohort. They matched 25 singleton cases of spontaneous preterm birth at 34 weeks or less and 50 uncomplicated term deliveries using factors such as maternal age, race, and gestational age of sampling. Circulating microparticles from these specimens were isolated and analyzed with quantitative proteomic liquid chromatography-mass spectrometry to identify potential protein biomarkers.

The researchers found that 62 of 132 identified proteins demonstrated robust power of detecting spontaneous preterm birth. These proteins were tied to biological processes of inflammation, wound healing, and the coagulation cascade. Using a multiplex of the candidate biomarkers had a sensitivity of 80 percent and a specificity of 83 percent with median area under the curve of 0.89 to predict spontaneous preterm birth, showing "strong potential" for informative risk stratification, the authors say.

"Differences in the protein content of microparticles likely represent an untapped source of information regarding biology of the maternal-fetal interface," write the authors, two of whom report financial ties to the diagnostics company NX Prenatal (Louisville, Ky.), which funded the study. "Some may suggest that we are premature in attempting the development of a predictive test without a universally agreed upon therapeutic modality… Such identification would allow the application of increased observation and the possible application of prophylactic therapies such as progesterone, which together may significantly improve the management of these patients."

Another company working towards the development of diagnostics capable of identifying personal risk of delivering early is Sera Prognostics (Salt Lake City). The company's PreTRM blood test is performed as early as 19 weeks and measures proteins associated with preterm birth. The proteins cover pathways associated with inflammation, hemorrhage, stress, uterine over-distention. PreTRM test is performed using liquid chromatography- tandem mass spectrometry. Researchers recently reported on the test's performance in an article published by AJOG and at the Pregnancy Meeting—the annual meeting of the Society for Maternal Fetal Medicine (Feb. 1-6; Atlanta, Ga.).

The 11-site PAPR (Proteomic Assessment of Preterm Risk) study enrolled 5,501 pregnant women (gestational age, 17 to 28 weeks between 2011 and 2013), representative of the United States population. Based on the researchers' previous proteomic findings, they validated a signature based on two proteins that are highly predictive of preterm birth risk: IBP4, insulin-like growth factor binding protein 4, and SHBG, sex-hormone binding globulin. The predictor (the ratio of IBP4/SHBG levels at 19 to 20 weeks gestation) had an area under the receiver operating characteristic curve value of 0.75 and sensitivity and specificity of 0.75 and 0.74, respectively.

"The classifier performance of the proteins in the PAPR study was excellent," said George R. Saade, M.D., from the University of Texas Medical Branch in Galveston and lead investigator. "These data demonstrate the powerful role proteomics can play in giving physicians a new tool to predict early an individual woman's risk of spontaneous preterm birth."

Preeclampsia
Preeclampsia is one of the most common complications during pregnancy, occurring in about one in every 20 third-trimester pregnancies. Similar to spontaneous preterm birth, there are currently no reliable biomarker tests for preeclampsia that have been accepted for wide clinical use, according to a review published in the fall of 2015 in the International Journal of Molecular Science.

"As preeclampsia cannot be predicted by previous obstetric history and risk factors alone, much research has focused on the identification of women at high risk of developing preeclampsia," writes co-author Louise Kenny. "This would allow more intensive monitoring of this high-risk group as well as targeted prophylactic intervention, timely diagnosis and treatment."

The researchers identified 147 studies that described 401 laboratory biomarkers. Placental growth factor (PlGF), pregnancy associated plasma protein A (PAPP-A), soluble fms-like tyrosine kinase (sFLT), and placental protein 13 (PP-13) were the most commonly studied biomarkers. The review found low predictive values for several individual biomarkers including a disintegrin and metalloprotease 12 (ADAM-12), inhibin-A, PAPP-A, PIGF, and PP-13. In pooled analysis, the sensitivity of all single biomarkers was 0.40 with a false positive rate of 10 percent. The area under the summary of receiver operating characteristics curve was 0.786. The authors concluded that, "although there are multiple potential biomarkers for preeclampsia, their efficacy has been inconsistent and comparisons are difficult because of heterogeneity between different studies."

Kenny's research has been licensed by Metabolomic Diagnostics (Ireland), which is currently conducting clinical trials to validate a preeclampsia test and has a test for preterm birth also in the pipeline. Early research showed promising results for the preeclampsia test, which is based on a unique set of 14 metabolites that can be identified from a blood sample taken at 15 weeks of gestation. The early evidence is based on samples from the Screening for Pregnancy Endpoints (SCOPE) study and bio-bank, which includes multiple samples from 6,000 participants in six countries. Next steps include further validation of this multi-metabolite based test in the large scale European, multicentre phase IIa clinical study IMproved PRegnancy Outcome by Early Detection (IMPROvED) which is currently recruiting first time pregnant women in five European countries.

Takeaway: Proteomics and metabolomics are enabling a new renaissance in the field of obstetrics. There is hope that new screening tests for spontaneous preterm birth and preeclampsia will reverse decades of stagnation in the pursuit of identifying women at early risk for these conditions.