Senhwa Biosciences Presents Clinical Data Abstract on Pidnarulex at 2024 ESMO Congress

• The study involved end-stage oncology patients with no other suitable treatment options.
• In this Phase Ib study, Pidnarulex (CX-5461) demonstrated acceptable clinical tolerability and showed preliminary signs of efficacy, even in patients who had previously failed treatment with PARP inhibitors.
• Out of 15 patients who were evaluable for drug response, 40% achieved clinical benefit, with stable disease (SD) being the best therapeutic response observed.

TAIPEI and SAN DIEGO, Sept. 9, 2024 /PRNewswire/ -- Senhwa Biosciences, Inc. (TPEx: 6492), a drug development company dedicated to developing first-in-class therapeutics for oncology, rare diseases, and infectious diseases, announced the presentation of a poster abstract of its investigational drug, Pidnarulex, at the 2024 European Society for Medical Oncology (ESMO) Congress. The abstract highlights Pidnarulex's demonstrated efficacy in treating various solid tumors harbouring BRCA1/2 or PALB2 gene defects. This significant milestone underscores the promising potential of Pidnarulex in the realm of precision medicine.

The findings, presented both on-site and online via the ESMO platform, involve patients with advanced-stage cancer who have undergone multiple prior treatments. Notably, a portion of the patients have achieved stable disease and are continuing to receive Pidnarulex as part of the ongoing clinical trial. This development marks a remarkable achievement for both Senhwa Biosciences and the collaborating Canadian and the US clinical team, reinforcing the drug's relevance in the evolving landscape of targeted cancer therapies.

The title of the poster abstract is "Phase 1b expansion study of CX-5461 in patients with solid tumours and BRCA2 and/or PALB2 mutation." The full abstract content has been published on the ESMO website at 00:05 CEST on September 9, 2024, at the following link: https://cslide.ctimeetingtech.com/esmo2024/attendee/confcal_2/presentation/list?q=631p. The trial report indicates that the preliminary results from Senhwa Biosciences' clinical trials of Pidnarulex, conducted in Canada and the USA, shows that out of the first 28 enrolled patients, 22 completed at least one cycle of treatment and were evaluated for dose-limiting toxicity (DLT). The patients had previously undergone multiple lines of cancer treatment, with a median of 6 lines (ranging from 2 to 10 lines) of prior therapy, including 77% of patients who had received platinum-based chemotherapy, 41% of patients who had been treated with bevacizumab, and 86% of patients who had previously received PARP inhibitors without success. These were end-stage oncology patients with no other suitable treatment options. The median number of Pidnarulex treatments received by the patients was 4 doses (ranging from 2 to 36 doses).

### Trial Results:

Among the 15 patients who were evaluable for drug response, 40% achieved clinical benefit, with stable disease (SD) being the best therapeutic response. Among these stable disease patients, there were 5 ovarian cancer patients, including 3 with BRCA1 somatic mutations, 1 with a BRCA1 germline mutation, and 1 with HRD-related gene mutations. All 5 patients had previously failed platinum chemotherapy and PARP inhibitor treatments, with 2 of them maintaining stable disease for at least 6 months following Pidnarulex treatment, offering renewed hope for advanced-stage ovarian cancer patients.

### Trial Objectives:

This clinical trial is designed as an open-label, multicenter, multinational study, divided into the Main Study Cohort and the Exploratory Cohort. It aimed to recruit patients with BRCA2 and/or PALB2 gene deficiencies from various tumor types (pancreatic cancer, ovarian cancer, prostate cancer, and breast cancer), as well as ovarian cancer patients with BRCA1 deficiencies and/or other HRD-related homologous recombination defects. The primary goal of the trial was to determine the recommended Phase II trial dose for patients with specific genetic deficiencies, while secondary endpoints include evaluating the safety, tolerability, and antitumor activity of Pidnarulex (CX-5461).

### Trial Conclusion:

This Phase Ib study demonstrated that CX-5461 exhibit acceptable clinical tolerability and shows preliminary signs of activity, even in patients who had previously failed treatment with PARP inhibitors. Photosensitivity was found to be manageable through preventive measures.

Currently, several PARP inhibitors have been approved by the FDA for the treatment of pancreatic, breast, ovarian, and prostate cancers with BRCA1/2 gene deficiencies. In addition to BRCA1/2, the PALB2 mutated gene represents a critical factor in in triple-negative breast cancer, ranking the third most significant gene associated with this subtype. Moreover, mutations in the PALB2 gene are also associated with a higher risk of developing ovarian and pancreatic cancers, further underscoring its importance in oncology.

Senhwa's Pidnarulex is a next-generation novel DDR drug with the potential to be developed as a rescue medication for patients who have developed resistance to PARP inhibitors. In preclinical studies, Pidnarulex has also demonstrated the ability to modulate tumor microenvironment, thereby enhancing sensitivity and efficacy of immunotherapy, including anti-PD-1 and anti-PD-L1. Senhwa looks forward to combining Pidnarulex with immunotherapy drugs such as Keytruda, which has been approved in the United States for the treatment of over 30 types of cancer. In 2023, Keytruda achieved global sales exceeding $25 billion, making it the highest-grossing drug worldwide. However, immunotherapy has its limitations, with only 20% of patients experiencing significant effects. If Pidnarulex can enhance the efficacy of immunotherapeutic agents, it is expected to provide new options for future treatment plans.