Whatever happened to Vincristine-loaded platelets?

Vincristine-loaded platelet infusion is a treatment where donor platelets are loaded with vincristine, a chemotherapy drug, and then infused into patients with ITP. The loaded platelets act as a "magic bullet" or "poison pill" as the specific lymphocytes that attack platelets are destroyed.

Numerous small but promising studies have been done over the years, going back at least as far as 1978, but seemingly nothing has come of it. For example:

www.ncbi.nlm.nih.gov/pubmed/16680744
Full text pdf at: onlinelibrary.wiley.com/doi/10.1002/ajh.20632/epdf
Am J Hematol. 2006 Jun;81(6):423-5.
Vincristine-loaded platelet infusion for treatment of refractory autoimmune hemolytic anemia and chronic immune thrombocytopenia: rethinking old cures.
Shvidel L1, Sigler E, Shtalrid M, Berrebi A.
Abstract
We report our experience with vincristine-loaded platelet infusion in patients with refractory immune thrombocytopenia (ITP), autoimmune hemolytic anemia (AIHA), and Evans syndrome. Ten patients with symptomatic thrombocytopenia and/ or hemolytic anemia who failed to respond to two to six different treatment modalities, including corticosteroids and splenectomy, were treated with infusion of vincristine-loaded platelets. Platelets were harvested by plateletpheresis from a healthy ABO compatible blood donor and incubated with 5 mg vincristine. Excess of vincristine was removed, and platelets were resuspended in 50 ml plasma and infused over 30 min. All 10 patients responded, and 6 of them achieved complete remission. The response was prompt, occurring 3-8 days after vincristine-loaded platelet infusion. Two patients with AIHA are still in remission 9 and 8 years posttreatment with no maintenance treatment. Three ITP patients achieved persisted partial response for 6 years, 5 years, and 11 months; in the remaining 5 patients the response lasted for 2-5 months. No side effects were seen. Our results suggest that this inexpensive and well-tolerated treatment modality may be a useful approach in patients with ITP and AIHA refractory to primary therapy.
PMID: 16680744

More recently, this technique was used to treat the canine version of ITP:

J Vet Sci. 2015 Mar; 16(1): 127–130.
Published online 2015 Mar 18. doi: 10.4142/jvs.2015.16.1.127 PMCID: PMC4367143
Application of vincristine-loaded platelet therapy in three dogs with refractory immune-mediated thrombocytopenia
Hyung-Jin Park, Ja-Won Kim, Kun-Ho Song, Kyoung-Won Seo

Abstract
Three dogs presented with refractory immune-mediated thrombocytopenia (IMT). All patients failed to respond to prednisone, which is considered a mainstay of immunosuppressive therapy. Vincristine-loaded platelets (VLPs), which act selectively on mononuclear phagocytes,were introduced. After the VLPs were transfused, two dogs responded quickly withimproved clinical signs while the third dogwith recurrent IMT was euthanized due to its deteriorating condition. This case report describes the efficacy of VLP therapy in refractory IMT patients.

This appears to be a safe and effective treatment, worthy of larger clinical trials.

www.mayoclinic.org/drugs-supplements/vincristine-intravenous-route/side-effects/drg-20066703

Personally I'd want to stay away from vincristine unless my life depended on it - I already have neuropathy and it is absolutely the pits.

3 dogs were given it?

10 patients given it - is that enough for a study to say yeah it works?

Careful Melinda. You know what happened the last time you complained about not enough evidence!

Seriously, though, there are not enough studies, but enough that further research should have been done. Perhaps there is a larger study with a negative outcome that didn't get published; negative results do not always get published.

The point of this approach is that Vincristine is not used systemically. It directly targets the cells which destroy platelets, so a much smaller quantity could be used. Thus the risk of side effects should be less.

Yikes. I'd have to be pretty desperate to try that one. Interesting theory, but I'd need to know what the potential side effects were. I don't see how that would be very successful.

You made me laugh Rob

I however still wouldn't want vincristine in any way shape or form unless it was a life or death situation. That's just me.

You know I just don't think a study with 3 dogs, one of which was put to sleep, hacks it - 3 dogs, when you consider all the humans in the world who have ITP.

I'm with Sandi.