A Study of [225Ac]Ac-AKY-2519 in Patients With Metastatic Castration-Resistant Prostate Cancer (BActinium-1)

May 6, 2026 updated by: Aktis Oncology, Inc.

BActinium-1: A Phase 1b, Multicenter, Open-label Study to Evaluate the Safety and Efficacy of Intravenous Administration of B7-H3 Radiopharmaceutical ([225Ac]Ac-AKY-2519) in Metastatic Castration-Resistant Prostate Cancer

This is a Phase 1b, multi-center, open-label study to evaluate the safety, tolerability, dosimetry, and pharmacokinetics (PK) of [64Cu]Cu-AKY-2519 and/or [225Ac]Ac-AKY-2519, as well as the preliminary anti-tumor activity of [225Ac]Ac-AKY-2519 in participants with metastatic castration-resistant prostate cancer (mCRPC) with and without prior exposure to 177Lu-PSMA-617 (PLUVICTO™).

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This Phase 1b study consists of a dose escalation portion and a backfill portion. The dose escalation portion will investigate ascending doses of [225Ac]Ac-AKY-2519 across two cohorts enrolling in parallel:

  • Cohort A: participants with metastatic castration-resistant prostate cancer (mCRPC) with NO prior exposure to 177Lu-PSMA-617 (PLUVICTO™) and
  • Cohort B: participants with metastatic castration-resistant prostate cancer (mCRPC) with prior exposure to 177Lu-PSMA-617 (PLUVICTO™)

The backfill portion may enrich in two select dose levels from each cohort (Cohort A: mCRPC 177Lu-PSMA-617 (PLUVICTO™)-naïve; Cohort B: mCRPC 177Lu-PSMA-617 (PLUVICTO™)-experienced) to gather further information on the safety and efficacy and to determine the recommended phase 2 dose (RP2D) for each cohort.

Study Type

Interventional

Enrollment (Estimated)

138

Phase

  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age ≥ 18 years
  • Histologic or cytologic confirmation of prostatic adenocarcinoma
  • ECOG Performance Status of 0 or 1
  • Adequate end-organ function
  • Ability to give informed consent and comply with study requirements
  • Patients with CNS metastases are eligible if they have received therapy and are neurologically stable, asymptomatic and not receiving corticosteroids
  • Castrate levels of serum testosterone (< 50 ng/dL)
  • Documented disease progression on most recent prior line of therapy, either by PSA or imaging-based progression
  • Cohort B: Received 2 or more prior doses of 177Lu-PSMA-617 (PLUVICTO)

Exclusion Criteria:

  • Prior treatment with more than 2 Androgen receptor pathway inhibitors (ARPIs) and/or more than 1 taxane-based therapy in the mCRPC setting

  • Prior treatment with a targeted radiotherapy

    o Exception: Cohort B is required to have had at least 2 prior doses of 177Lu-PSMA-617 (PLUVICTO)

  • Prior treatment with a B7-H3 targeted therapy
  • Received an investigational agent within the previous 28 days
  • Impaired cardiac function or clinically significant cardiac disease
  • Concurrent serious medical condition that would impair study participation or impact the assessment of treatment related toxicity

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: [225Ac]Ac-AKY-2519
Drug: [225Ac]Ac-AKY-2519 (therapeutic)
[225Ac]Ac-AKY-2519 Injection
Drug: [64Cu]Cu-AKY-2519 (imaging)
[64Cu]Cu-AKY-2519 Injection

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Occurrence of adverse events by severity and occurrence of serious adverse events (SAEs) in participants who received [225Ac]Ac-AKY-2519
Time Frame: Up to 30 days following last administration of [225Ac]Ac-AKY-2519
An AE is defined as any untoward medical occurrence in a participant administered study drug, which does not necessarily have to have a causal relationship with the study drug. The number of patients experiencing an AE and the number of patients experiencing an SAE will be reported. Up to 30 days following last administration of [225Ac]Ac-AKY-2519
Up to 30 days following last administration of [225Ac]Ac-AKY-2519
Occurrence of dose-limiting toxicity (DLT) in mCRPC participants with and without prior 177Lu-PSMA-617 exposure
Time Frame: From first administration of [225Ac]Ac-AKY-2519 to the end of Cycle 1 (each cycle is 28 days)
Dose-limiting toxicities (DLTs) is defined as any predefined AE occurring during the DLT observation period, except those that are clearly and incontrovertibly due to extraneous circumstances. The number of patients who experience a DLT will be reported separately for each cohort and by dose level within each cohort.
From first administration of [225Ac]Ac-AKY-2519 to the end of Cycle 1 (each cycle is 28 days)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Occurrence of adverse events by severity and occurrence of serious adverse events (SAEs) in participants who received [64Cu]Cu-AKY-2519
Time Frame: Up to 30 days following last administration of [64Cu]Cu-AKY-2519
An AE is defined as any untoward medical occurrence in a participant administered study drug, which does not necessarily have to have a causal relationship with the study drug. The number of patients experiencing an AE will be reported.
Up to 30 days following last administration of [64Cu]Cu-AKY-2519
Objective Response Rate (ORR)
Time Frame: Up to 30 days following last administration of [225Ac]Ac-AKY-2519
ORR is defined as the percentage of patients who achieved a best overall response of confirmed Complete Response (CR) or Partial Response (PR), as determined by the investigator based on PCWG3-modified RECIST v1.1.
Up to 30 days following last administration of [225Ac]Ac-AKY-2519
Duration of Response (DoR)
Time Frame: Up to 5 years after first administration
Duration of Response (DoR) is defined as the time from the date of the first documentation of objective response (complete response [CR] or partial response [PR]) to the date of the first objective documentation of progressive disease (PD) or death due to any cause.
Up to 5 years after first administration
Progression-Free Survival (PFS)
Time Frame: Up to 5 years after first administration
PFS is defined as the time from treatment initiation to the first documented disease progression per RECIST 1.1 or death due to any cause, whichever occurs first.
Up to 5 years after first administration
Prostate Specific Antigen (PSA) >= 50% Response Rate (PSA50)
Time Frame: Up to 30 days following last administration of [225Ac]Ac-AKY-2519
Will assess PSA decline of >= 50% from baseline (PSA50), using the Prostate Cancer Working Group 3 (PCWG3) criteria.
Up to 30 days following last administration of [225Ac]Ac-AKY-2519
Prostate Specific Antigen (PSA) >= 90% Response Rate (PSA90)
Time Frame: Up to 30 days following last administration of [225Ac]Ac-AKY-2519
Will assess PSA decline of >= 90% from baseline (PSA90), using the Prostate Cancer Working Group 3 (PCWG3) criteria.
Up to 30 days following last administration of [225Ac]Ac-AKY-2519

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Aktis Oncology, Inc.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

July 1, 2026

Primary Completion (Estimated)

December 1, 2027

Study Completion (Estimated)

June 1, 2032

Study Registration Dates

First Submitted

May 6, 2026

First Submitted That Met QC Criteria

May 6, 2026

First Posted (Actual)

May 12, 2026

Study Record Updates

Last Update Posted (Actual)

May 12, 2026

Last Update Submitted That Met QC Criteria

May 6, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • AKY-2519-01

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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