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Allschwil, Switzerland, August 3, 2021

Polyphor provides final update on the Phase III FORTRESS study of balixafortide in patients with advanced HER2 negative breast cancer

- Primary endpoint of the study progression free survival (PFS) was not met

- Pre-specified interim analysis of overall survival (OS) showed no statistically significant differences between study groups

Polyphor AG (SIX: POLN) today announced that its global Phase III FORTRESS study, evaluating balixafortide (POL6326) in combination with eribulin for the treatment of patients with HER2 negative, locally recurrent or metastatic breast cancer, did also not meet its primary endpoint. As communicated, the analysis was conducted following the company's decision to initiate the closure of the FORTRESS study.

The FORTRESS study investigates the efficacy and safety of the combination of balixafortide and eribulin versus eribulin monotherapy in patients with HER2 negative metastatic breast cancer with progressive disease after one to four lines of chemotherapy. Progression free survival (PFS) is the key primary endpoint of the study. 432 patients were included in the FORTRESS study, thereof 348 having had at least two lines of prior chemotherapy, a prespecified subgroup of the study.

The study did not meet its primary endpoint of PFS in the overall population (n=432 patients): HR=1.10 (0.85, 1.41); p=0.445; median PFS: 3.5 m (B+E) vs. 4.0 m (E) and also not in the patients with at least 2 prior lines of chemotherapy according to the assessment of the blinded independent review committee (n=348 patients): HR=1.07 (0.81, 1.41); p=0.6158; median PFS: 3.5 m (B+E) vs. 4.0 m (E). Investigator assessment of PFS was consistent with the independent review committee analysis (HR=0.99 for the overall population and HR=1.05 for the > second line population).

At the time of the PFS analysis, a pre-specified interim analysis of overall survival (OS) was conducted as well. There were no statistically significant differences for survival in the overall population (230 events): HR=1.08 (0.71,1.63); p=0.5897; median OS: 10.9 m (B+E) vs. 11.7 m (E) or in the > second line population (181 events): HR=1.08 (0.66, 1.77); p=0.6126; median OS: 11.0 m (B+E) vs. 11.2 m (E).

The analysis of the safety and tolerance of balixafortide in combination with eribulin in the FORTRESS study was consistent with the previously reported safety profile with a numerically higher number of patients having had serious adverse events (28.4% B+E vs. 26.5% E) or adverse events of a grade 3 or higher severity (68.3% B+E vs. 63.7% E).

Based on these results, the FORTRESS study will be closed and the pre-specified secondary efficacy analysis of OS after reaching 284 events in the overall population will not be performed.

"We are disappointed with the results of the FORTRESS study given the high unmet medical need for patients with advanced breast cancer," says Frank Weber, CMO of Polyphor. "As previously communicated, we will now close the study. We thank all the patients, investigators and healthcare professionals as well as our employees for their active participation in this study."

As recently announced, the board of directors has extended the period for strategic evaluation of all options for the future of the Company by not later than end of August.

About the FORTRESS study
The FORTRESS study (POL6326-009) is an international, multicenter, randomized active-controlled, open-label Phase III trial which investigates the efficacy, safety and tolerability of intravenous balixafortide given with eribulin versus eribulin alone in the treatment of HER2 negative, locally recurrent or metastatic breast cancer. The study had randomized 432 patients with HER2 negative MBC with at least 344 patients receiving third or subsequent line and 88 patients receiving second line chemotherapy.

About balixafortide
Balixafortide (POL6326) is a potent, specific, and highly selective antagonist of the chemokine receptor CXCR4, a G-protein coupled receptor (GPCR) that regulates the trafficking and homing of both cancer cells and cells of the patient's immune system.

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About Polyphor
Polyphor is a research driven clinical-stage, Swiss biopharmaceutical company committed to discovering and developing novel molecules in oncology and antimicrobial resistance leveraging the company's proprietary macrocyclic peptide technology platform. Polyphor is based in Allschwil near Basel and is listed on the SIX Swiss Exchange (SIX: POLN). For more information, please visit www.polyphor.com.

Disclaimer
This press release contains forward-looking statements which are based on current assumptions and forecasts of the Polyphor management. Known and unknown risks, uncertainties, and other factors could lead to material differences between the forward-looking statements made here and the actual development, in particular Polyphor's results, financial situation, and performance. Readers are cautioned not to put undue reliance on forward-looking statements, which speak only of the date of this communication. Polyphor disclaims any intention or obligation to update and revise any forward-looking statements, whether as a result of new information, future events or otherwise.