For
CLARITY (which helps simple minds like mine), I think it's worth making clear that TLX591 (from Telix) and lutetium 177 (on the Pluvicto product from Norvatis) referred to here, are Therapies (and not diagnostics). Hence, they are not related to this CLARITY announcement (about diagnostics).
The relevant Clarity product that we need to compare those 2 products with is
67Cu-Sar-bisPSMA, which is being evaluated under the
SECuRE trial. There is a whole lot more that we can discuss on that topic, including;
EFFECTIVENESS:- 67Cu-Sar-bisPSMA is in early trials (dose escalation / dose expansion), but what we know so far from Cohorts 1 and 2 is that the effectiveness is unprecedented (1). Everyone treated and so far reported, responded with PSA levels dropping significantly. In some cases, the PSA dropped over 95%. The patients who received additional doses under EAP had more impressive responses: undetectable PSA and undetectable disease on Imaging!
- TLX591 is in Phase 3 trials (2). We already know that it too has shown PSA reductions, but the >50% PSA decline was achieved by just 11.4% (compared to everyone so far reported on 67Cu-Sar-bisPSMA). Radiologically, the best that TLX591 has shown is disease regression (9.1%), and stable disease (54.5%). 45.4% had disease progression.
- Overall survival is a long term outcome - not able to compare. But TLX591 has been better than Pluvicto.
SAFETY PROFILES- So far, with the limited data, 67Cu-Sar-bisPSMA has had unprecedented levels of safety, with 4GBq, 8GBq and 12GBq doses of 67Cu-SAR-bisPSMA showing no dose limiting toxicities (DLTs).
- While TLX591 had 61.1% showing haematological toxicities as well as many other complications. See abstract below.
TLX591 will make it across the line: it has advantages over Pluvicto, and it's in Phase 3 (ahead of 67Cu-Sar-bisPSMA). But,
67Cu-Sar-bisPSMA looks to be the Best In Class, so I expect it will get there too.
There is a lot of cancer around! Good times ahead!
You will be told that PSA reduction does not matter: Why did you use it as a measure of effectiveness if it doesn't matter?
REFERENCES(1) SECuRE: A dose escalation/expansion study to assess the anti-tumor efficacy of 67Cu-SAR-bisPSMA in patients with metastatic castrate-resistant prostate cancer; Geoffrey Johnson1, Eva Lengyelova2, Luke T. Nordquist3, et al.
https://www.claritypharmaceuticals.com/wp-content/uploads/2024/07/SNMMI-2024-SECuRE1-Final.pdf(2) Lutetium-177 Labelled Anti-PSMA Monoclonal Antibody (Lu-TLX591) Therapy for Metastatic Prostate Cancer: Treatment Toxicity and Outcomes; Hanh Nguyen, Kathryn Hird, et al.
https://pubmed.ncbi.nlm.nih.gov/38446353/An Abstract with the TLX591 paper is included.
(20min delay)