From Urine-Derived To Recombinant Precision: KLK1 Reimagined For Preeclampsia
By Ray Dogum, Chief Editor, Drug Discovery Online
In addition to celebrating our mothers on May 10 this year, May 10-16 is also National Women’s Health Week, and May is Preeclampsia Awareness Month, so I am pleased to be able to share this story at such an opportune time.
Drug discovery often advances not by uncovering entirely new biology, but by revisiting established science with modern tools. Few stories illustrate this better than the journey of recombinant human kallikrein‑1 (rhKLK1), a naturally occurring protein now being advanced in the clinic for preeclampsia and acute ischemic stroke.
At the center of this effort is DiaMedica Therapeutics, which has spent more than a decade solving a problem that defeated some of the largest pharmaceutical companies: how to manufacture an active recombinant version of KLK1. As CEO Rick Pauls explains to Drug Discovery Online, “The problem we’ve solved is being able to manufacture a recombinant form of this protein that others weren’t able to do.”
An Old Protein with a Long Clinical History
KLK1 is not new to medicine. Porcine pancreas-derived forms were first investigated by Bayer in the 1940s for hypertension. In Asia, particularly China, crude KLK1 preparations have been used clinically for decades. There, a human urinary form—extracted directly from community collected urine—has also been used extensively, primarily for acute ischemic stroke.
“In China, they’re approaching a million patients a year being treated with the human urine form,” Pauls notes, underscoring the breadth of real‑world exposure that informs the biology.
The manufacturing reality behind that statistic is striking. The protein is isolated from fresh human urine—often collected from public restrooms—processed within a narrow time window and then purified at industrial scale. According to Pauls, producing enough drug requires urine volumes “on the order of a tanker per patient,” highlighting both the ingenuity and the limitations of the approach. “Shanghai Pharma is the company there that's currently marketing the urinary form,” Pauls adds.
While effective, urine‑derived biologics present inherent challenges: batch variability, supply constraints, and the risk of disease transmission. These issues make such crude preparations incompatible with modern Western regulatory standards. “Today, it’s not possible to bring a urine or porcine form to the West because you can’t provide assurance around disease transmission or batch‑to‑batch consistency,” Pauls explains.
The Drug Discovery Challenge: Activity, Not Expression
From a drug discovery standpoint, the core challenge was not producing KLK1—it was producing an active form. Multiple groups, including Amgen (who patented the production process) decades ago, succeeded in expressing recombinant human KLK1 but failed to clinically reproduce its biological activity.
The breakthrough came when DiaMedica focused on glycosylation. KLK1’s enzymatic function depends not only on its amino acid sequence, but on how sugar moieties are attached. “It wasn’t until we started doing work on the glycosylation—how the sugars are attached—that we were able to get an active form of the protein,” Pauls says.
The company ultimately discovered that a precise 50-50 mixture of high and low glycoforms was required for activity—an insight that proved non-obvious and patentable. Two additional amino acid substitutions improved manufacturability without compromising function, enabling scalable production with “very similar enzymatic activity.”
This early discovery work was neither quick nor linear. “It probably took us three to four years to actually make it an active molecule,” Pauls reflects.
Why Preeclampsia?
Preeclampsia remains one of the most dangerous complications of pregnancy, characterized by new‑onset hypertension, organ dysfunction, and placental insufficiency. The underlying pathology involves a hypoxic placenta that releases anti‑angiogenic and inflammatory factors, driving systemic maternal disease.
Despite its severity, treatment options remain limited, with the delivery of the premature baby often seen as the only definitive intervention.
DiaMedica’s rhKLK1 is designed to address this biology directly. KLK1 promotes localized vasodilation and improved blood flow. In early clinical studies, the therapy has demonstrated reductions in maternal blood pressure and dilation of intrauterine arteries, improving placental perfusion.
“If we can get more blood flow to the placenta, we may be targeting the root cause of the disease, which is a hypoxic placenta,” Pauls explains.
Crucially, rhKLK1 is a large protein that, in early studies, has been shown not to cross the placental barrier, minimizing fetal exposure. This distinguishes it from many small‑molecule antihypertensives—such as ACE inhibitors and ARBs—which are contraindicated in pregnancy because they can cross the placenta and harm the fetus.
Clinical Validation Studies
DiaMedica’s development strategy builds on decades of clinical use of urinary KLK1 in China, but translates that experience into controlled, mechanism-driven trials with their DM199 (rinvecalinase alfa) compound for recombinant human KLK1 (rhKLK1).
The goal is not replication, but replacing a variable biologic source with a scalable, well‑characterized therapeutic.
In preeclampsia, this is being evaluated in a multi‑part Phase 2 program that integrates dose‑finding with early efficacy. Ongoing studies include IV and subcutaneous dosing, transitioning toward a clinically intended regimen of subcutaneous administration every three days through delivery.
Key endpoints include maternal blood pressure, uterine artery pulsatility index, and angiogenic biomarkers such as sFlt‑1 and placental growth factor, alongside gestational outcomes. Interim data show rapid, dose‑dependent reductions in blood pressure and improved uteroplacental perfusion, consistent with a vasoactive and endothelial mechanism. Parallel cohorts in early‑onset disease and fetal growth restriction are being used to refine dose selection ahead of a potential Phase 3 program.
In acute ischemic stroke, the program has progressed to a global Phase 2/3 adaptive trial (ReMEDy2). This randomized, double‑blind, placebo‑controlled study enrolls patients with moderate stroke and evaluates an IV loading dose (0.5 μg/kg) followed by twice‑weekly subcutaneous dosing for three weeks, with functional outcomes assessed at 90 days. An interim analysis after approximately 200 patients enables futility assessment and sample size adjustment, aligning clinical execution with adaptive development principles.
Re‑Engineering Established Science for Modern Medicine
The story of rhKLK1 underscores a broader lesson in drug discovery: innovation does not always require new targets. It can also mean applying modern manufacturing techniques, regulatory rigor, and clinical discipline to well‑validated biology.
“There are hundreds of publications spanning decades on this protein. The science has been around a long time—we just figured out how to manufacture an active recombinant form,” Pauls concludes.
In doing so, DiaMedica has transformed a crude, supply-limited biologic into a scalable, precise therapy. It bridges decades of clinical observation with modern biotechnology and offers hope for a future where more mothers can reach delivery safely, with healthier outcomes for both mother and baby.