Qurient Doses First Patient in Phase 2 Trial of Mocaciclib for CDK4/6 Inhibitor-Resistant HR-Positive Breast Cancer
Qurient Co., Ltd. has announced a major clinical development milestone with the dosing of the first patient in a Phase 2 study evaluating mocaciclib (Q901) in combination with fulvestrant for the treatment of hormone receptor-positive (HR-positive) breast cancer. The study is specifically designed for patients whose disease has progressed following treatment with CDK4/6 inhibitor-based therapies, a growing population of patients facing limited therapeutic options after developing resistance to current standards of care.
The initiation of patient dosing marks an important step in the advancement of mocaciclib, an investigational, highly selective covalent inhibitor of cyclin-dependent kinase 7 (CDK7). The therapy is being developed to address significant unmet medical needs in advanced solid tumors, particularly cancers that have developed resistance to existing targeted treatments.
For patients with HR-positive, HER2-negative metastatic breast cancer, the introduction of CDK4/6 inhibitors dramatically improved outcomes over the past decade, becoming a foundational component of treatment when combined with endocrine therapy. However, despite the substantial benefits provided by these therapies, many patients ultimately experience disease progression due to either intrinsic resistance or the development of acquired resistance mechanisms over time.
Qurient believes mocaciclib may offer a new therapeutic strategy capable of overcoming these resistance pathways by simultaneously targeting cell cycle regulation and cancer-driving transcriptional programs.
Addressing a Growing Clinical Challenge
Hormone receptor-positive breast cancer is the most common subtype of breast cancer worldwide. While advances in endocrine therapy and targeted treatments have significantly improved patient outcomes, resistance remains one of the greatest challenges in the management of advanced disease.
CDK4/6 inhibitors, including several approved therapies now widely used in combination with endocrine treatments, have transformed the treatment landscape for patients with metastatic HR-positive, HER2-negative breast cancer. These agents work by blocking cyclin-dependent kinases 4 and 6, key proteins involved in regulating the transition of cells through the cell cycle.
By inhibiting these kinases, cancer cell proliferation can be slowed or halted, leading to prolonged disease control and improved progression-free survival for many patients.
However, the effectiveness of CDK4/6 inhibitors is not permanent. Over time, many tumors develop mechanisms that enable them to bypass the blockade imposed by these drugs. Once resistance emerges, treatment options become more limited, and patients often require additional therapies with varying levels of effectiveness.
The growing number of patients whose cancers have become resistant to CDK4/6 inhibitors has created an urgent need for novel therapeutic approaches capable of addressing the biological pathways that drive treatment failure.
It is within this context that Qurient is advancing mocaciclib.
First Patient Dosed in Phase 2 Study
The newly initiated Phase 2 clinical trial will evaluate mocaciclib in combination with fulvestrant, a selective estrogen receptor degrader commonly used in patients with advanced HR-positive breast cancer.
The study is focused specifically on individuals whose tumors have demonstrated resistance to prior CDK4/6 inhibitor-containing regimens. Researchers will assess the safety, tolerability, and antitumor activity of the combination while seeking to determine whether CDK7 inhibition can overcome established resistance mechanisms.
The dosing of the first patient represents the beginning of a critical stage in the clinical development program. Data generated from the trial will help determine whether mocaciclib can provide meaningful clinical benefits for patients who have exhausted current standard treatment options.
According to Qurient leadership, the trial is designed to translate growing scientific insights into CDK7 biology into potential therapeutic outcomes for patients with advanced breast cancer.
A Novel Approach Through CDK7 Inhibition
Unlike CDK4/6 inhibitors, which target specific components of the cell cycle machinery, mocaciclib focuses on CDK7, a kinase that occupies a unique and highly influential position within cancer cell biology.
CDK7 serves two major biological functions. It acts as a master regulator of cell cycle progression while also playing a critical role in controlling gene transcription. This dual functionality makes it an especially attractive therapeutic target for cancers that have developed alternative pathways to evade existing treatments.
Mocaciclib has been engineered as a highly selective and potent covalent inhibitor of CDK7, allowing sustained inhibition of the target enzyme while minimizing activity against unrelated proteins.
Researchers believe this selectivity may help maximize therapeutic effectiveness while supporting an acceptable safety profile.
Targeting Cell Cycle Escape Mechanisms
One of the most important scientific rationales for mocaciclib involves its ability to interfere with cell cycle escape mechanisms that frequently emerge following CDK4/6 inhibitor treatment.
CDK7 functions as the CDK-activating kinase (CAK), a master regulator responsible for activating several other cyclin-dependent kinases, including CDK1, CDK2, CDK4, and CDK6.
In many cases of CDK4/6 inhibitor resistance, cancer cells adapt by activating alternative pathways that allow them to continue dividing despite inhibition of CDK4 and CDK6.
Two of the most common resistance mechanisms involve loss of retinoblastoma (RB) protein function and activation of the Cyclin E-CDK2 signaling axis.
When these alterations occur, cancer cells effectively bypass the therapeutic blockade created by CDK4/6 inhibitors and re-enter the cell cycle, allowing continued tumor growth and disease progression.
By inhibiting CDK7, mocaciclib may prevent activation of CDK2 and other downstream kinases that drive these escape routes.
As a result, researchers believe the therapy could restore control over cell cycle progression and suppress tumor proliferation even in cancers that no longer respond to conventional CDK4/6 inhibition.
Disrupting Cancer-Promoting Gene Transcription
Beyond its role in cell cycle regulation, CDK7 also plays a critical role in gene transcription.
The kinase is a key component of the transcription factor IIH (TFIIH) complex, which helps regulate the transcription of numerous genes required for cancer cell survival and growth.
This second mechanism of action may provide another important advantage for mocaciclib.
Many aggressive cancers become dependent on oncogenic transcription factors such as MYC and E2F, which regulate the expression of genes involved in proliferation, metabolism, and survival. These transcriptional programs often contribute to treatment resistance and disease progression.
Mocaciclib has been designed to selectively suppress transcriptional activity associated with these cancer-promoting pathways.
By disrupting the transcription of key oncogenic drivers, the therapy may reduce cancer cells’ ability to maintain growth and survival programs that support resistance to therapy.
Addressing PTEN-PI3K/AKT Pathway Activation
Another important rationale for mocaciclib lies in its potential impact on the PTEN-PI3K/AKT signaling pathway.
Activation of this pathway is one of the most frequently observed mechanisms of resistance in HR-positive breast cancer. Alterations affecting PTEN function or enhanced PI3K/AKT signaling can promote tumor survival and allow cancer cells to evade the effects of endocrine therapy and CDK4/6 inhibitors.
Research conducted by Qurient suggests that CDK7 inhibition may suppress the expression of genes activated through the PTEN-PI3K/AKT pathway.
By targeting this critical resistance mechanism, mocaciclib could potentially neutralize one of the major biological drivers of treatment failure in advanced breast cancer.
This multi-dimensional approach—combining cell cycle inhibition, transcriptional repression, and interference with survival signaling pathways—distinguishes mocaciclib from many currently available therapies.
Leadership Highlights the Promise of Mocaciclib
Kiyean Nam, Ph.D., Chief Executive Officer of Qurient, described the first patient dosing as a significant milestone for the company and its broader mission of developing innovative therapies for patients with limited treatment options.
According to Dr. Nam, many patients with HR-positive breast cancer eventually exhaust available standard-of-care therapies, creating a need for new approaches capable of addressing the complex biology underlying resistance.
He emphasized that mocaciclib’s unique mechanism of action positions it as a potentially valuable option for patients whose tumors have developed alternative pathways to bypass CDK4/6 inhibition.
Dr. Nam also highlighted the company’s growing understanding of CDK7 biology and expressed optimism that ongoing research could ultimately translate into meaningful clinical benefits for patients facing advanced disease.
The launch of the Phase 2 trial represents an important advancement in the development of mocaciclib and reflects broader efforts within oncology to address resistance mechanisms that emerge after targeted therapy treatment.
As more patients receive CDK4/6 inhibitors earlier in the course of disease management, the number of individuals requiring effective post-CDK4/6 treatment options continues to increase. Consequently, therapies capable of overcoming established resistance pathways are becoming an increasingly important area of research.
Through its selective inhibition of CDK7, mocaciclib aims to address multiple biological mechanisms responsible for treatment failure, including cell cycle escape, transcriptional dependency, and activation of survival signaling pathways.
The first patient dosing marks the beginning of a new stage in evaluating whether this scientific strategy can translate into improved outcomes for patients with hormone receptor-positive breast cancer who have exhausted current therapeutic options. As the Phase 2 study progresses, investigators will closely monitor safety and efficacy outcomes to determine whether mocaciclib can emerge as a promising new treatment option in the evolving landscape of precision oncology.
About Mocaciclib (Q901)
Mocaciclib (Q901) is an intravenously administered, highly selective covalent CDK7 inhibitor currently advancing through Phase 1/2 clinical trials (NCT05394103). In addition to its potential as a monotherapy in HR+ breast cancer and other advanced solid tumors, mocaciclib has demonstrated profound synergy in preclinical models when used in combination with Topoisomerase 1 inhibitor-based antibody-drug conjugates (TOP1i-ADCs) and immune checkpoint inhibitors.
About Qurient
Qurient Co., Ltd. is a clinical-stage biopharmaceutical company focused on the discovery and development of novel therapeutics for oncology and inflammatory diseases. Utilizing a network-centric research and development model, Qurient successfully collaborates with top-tier research institutes and global pharmaceutical companies to translate innovative science into impactful medicines.
