Japanese Foundation for Cancer Research

The goal of this clinical study is to determine whether monitoring ctDNA and treating patients who become ctDNA-positive with abemaciclib can help prevent the recurrence of hormone receptor-positive, HER2-negative breast cancer after curative surgery and standard therapy. The study will also assess the safety of abemaciclib and the medical problems that may occur during treatment. Participants will receive routine follow-up after surgery, undergo regular blood tests to measure ctDNA, and, if ctDNA becomes positive, receive abemaciclib for a defined treatment period with scheduled clinic visits for examinations and safety assessments. Researchers will evaluate recurrence-free survival, distant recurrence-free survival, adverse events, the time between ctDNA positivity and clinical recurrence, and the rate of ctDNA clearance at the end of abemaciclib therapy.

* Breast cancer is histologically divided into non-invasive (approximately 10%) and invasive (approximately 90%), with invasive cancer being the target of chemotherapy. Invasive carcinoma is classified into four subtypes according to the expression levels of hormone receptor (HR) and human epidermal growth factor receptor type 2 (HER2). Among them, triple negative breast cancer accounts for 10% of invasive cancers and is the subtype with the poorest prognosis.
* For triple negative breast cancer that is operable, chemotherapy with pembrolizumab is administered either preoperatively or postoperatively (perioperative period). For recurrent triple negative breast cancer , combination chemotherapy with multiple agents is the standard of care, especially in the case of PD-L1-positive patients, chemotherapy with an immune checkpoint inhibitor related to PD-1 (pembrolizumab or atezolizumab) is administered.
* Although the KEYNOTE355 trial demonstrated the efficacy of pembrolizumab plus paclitaxel therapy in patients with PD-L1-positive triple negative breast cancer in postoperative relapse, this trial did not include patients who received pembrolizumab in the perioperative period. Therefore, it is not known if there is any benefit to re-administering pembrolizumab to these patients after relapse.
* Bevacizumab is used as standard therapy for triple negative breast cancer in combination with paclitaxel. Bevacizumab itself is an anti-tumor agent that inhibits angiogenesis, but has also been reported to activate immunity against cancer, suggesting that it may enhance the effect of pembrolizumab.
Based on the above, the investigators planned this trial to evaluate whether pembrolizumab + paclitaxel + bevacizumab therapy is more effective than pembrolizumab + paclitaxel therapy in PD-L1-positive triple negative breast cancer patients who relapse after receiving immune checkpoint inhibitors in the perioperative period.

Tankyrase, the fifth and sixth members of the poly(ADP-ribose) polymerase (PARP) family (PARP-5a/b), is responsible for poly(ADP-ribosyl)ation (PARylation), and was originally identified as a factor that promotes the function of telomerase, an enzyme that elongates telomeres. Subsequently, it was reported that tankyrase enhances Wnt/beta-catenin signaling by PARylation and subsequent degradation of AXIN, a negative regulator of Wnt/beta-catenin signaling, suggesting that tankyrase inhibitors may be a new treatment for colorectal cancer.
RK-582 was discovered through lead optimization from a tankyrase inhibitor that suppresses the growth of human colorectal cancer cells. It was confirmed that RK-582 selectively inhibited tankyrase among the PARP family enzymes, suppressed the growth of Wnt/beta-catenin signal-dependent human colorectal cancer cells at both the levels of cultured cells and xenograft tumors in immunodeficient mice, and accumulated AXIN to decrease beta-catenin and downregulate the target gene expression as pharmacodynamic biomarkers.
Based on these findings, RK-582 is thought to have potential as a new treatment for colorectal cancer patients. At present, however, the efficacy and safety of RK-582 in humans have not been confirmed. Thus, this clinical trial is conducted with the aim of investigating the tolerability and safety of RK-582 for patients with unresectable advanced or recurrent colorectal cancer as a first-in-human trial, in which RK-582 is administered to humans for the first time.