ACER-801 (osanetant) for Prostate Cancer

ACER-801 (osanetant) for Prostate Cancer

ACER-801 (osanetant) is an investigational, novel, non-hormonal, neurokinin 3 receptor (NK3R) antagonist currently being evaluated as a potential treatment option for men with adenocarcinoma of the prostate.

Rationale for ACER-801 Treatment for Prostate Cancer
Prostate cancer is a hormonally driven cancer, and the management of this disease for many men is through suppression of testosterone production – called androgen deprivation therapy (ADT). Currently, most men on ADT are treated with medications that suppress hormone production which can cause dysfunctional thermoregulation and development of vasomotor symptoms (VMS), also known as hot flashes. Up to 75% of men on ADT experience VMS, resulting in high rates of distress and ADT treatment noncompliance, with approximately 20% of men with high-risk prostate cancer prematurely discontinuing ADT.1 Early pharmacokinetic studies in men and women with various NK3R antagonists have shown an inhibitory effect on the levels of luteinizing hormone and testosterone. However, the degree of effect relative to a therapeutic goal of castrate levels of testosterone (≤ 50ng/mL) remains unexplored.2,3 A non-hormonal treatment to lower testosterone levels and manage induced VMS is needed as estrogen is contraindicated for the management of VMS in patients with hormone-positive tumors, including breast and prostate tumors.

ACER-801 Registration Plan (Prostate Cancer)
In Jan. 2023, Acer announced the initiation of two Phase 2, single-arm investigator-sponsored trials evaluating ACER-801 (osanetant) in men with adenocarcinoma of the prostate. The POSH-MAP (Pilot of Osanetant for Severity of Hot Flashes in Men with Adenocarcinoma of the Prostate) and PORT-MAP (Pilot of Osanetant to Reduce Testosterone in Men with Adenocarcinoma of the Prostate) trials are evaluating ACER-801’s (osanetant) ability to reduce hot flashes and its potential as neoadjuvant therapy in men with prostate cancer. The trials are sponsored and conducted by The University of Kansas Cancer Center in partnership with Acer.

The POSH-MAP trial will evaluate the ability of ACER-801 to reduce hot flash frequency and severity and improve quality of life measures in men with prostate cancer following 28 days of therapy. Approximately 10 participants will receive 200mg of osanetant twice daily. Following the completion of treatment on day 28 participants will re-test hormone levels and report final patient outcome measures. More information on this trial can be found here

The second trial, PORT-MAP, will evaluate the ability of ACER-801 to suppress testosterone production in men with prostate cancer within 28 days prior to a planned prostatectomy. Approximately 10 participants will receive 200mg of osanetant twice daily for 28 days, followed by a one week wash out period. Following the one week wash out period, patients will undergo a prostatectomy between days 35-39. The overall effect of osanetant on testosterone levels and the proportion of men achieving castrate levels of testosterone (<50ng/ml) will be assessed, with hormone level assessment occurring on days 2, 3, 14, 28 and day 77. More information on this trial can be found here.

Additional information on the ACER-801 program can be found in our current corporate presentation.

ACER-801 is an investigational drug in the U.S. and is not currently FDA approved for any indication. There is no guarantee that this product candidate will receive regulatory authority approval in any territory or become commercially available for any indications.


  1. Trinity Partners 2020
  2. Challapalli, Amarnath, et al. “Evaluating the Prevalence and Predictive Factors of Vasomotor and Psychological Symptoms in Prostate Cancer Patients Receiving Hormonal Therapy: Results from a Single Institution Experience.” Clinical and Translational Radiation Oncology, Elsevier, 21 Mar. 2018
  3. Prague J. et al. Neurokinin 3 receptor antagonism rapidly improves vasomotor symptoms with sustained duration of action. Menopause. 2018 Aug; 25(8): 862–869.