Clinical Trial: Neuroendocrine Cancer drug in the pipeline – Fosbretabulin Tromethamine CA4P (incl combo with Everolimus)

{NEW} added 4 June 2019

From ASCO 2019 conference extract: Of the 17 patients enrolled, 16 completed the 12-week trial. One patient was not evaluable due to noncompliance. No DLTs were observed at day 21. The highest dose of 10 mg daily oral everolimus in combination with weekly 60mg/m2 IV fosbretabulin is the RP2D. No grade 4 or 5 toxicities were noted. Grade 3 toxicities were seen in 5 patients; abdominal pain and hyperglycemia (not related to study drug), fatigue (possibly related), decreased lymphocyte count and anemia (related). Several patients had delay in treatment due to grade 2 AE’s (GI symptoms, rash, thrombocytopenia) and one patient was unable to complete treatment due to pneumonitis. All evaluable patients except one had stable disease at 3 months. One patient showed SD but non target lesion demonstrated PD. One patient had > 30% decrease in tumor size but overall sum of lesions showed SD. A detailed table with all grade toxicities and waterfall plot of RR will be presented at the meeting. Ten mg PO daily everolimus plus 60 mg/m2 fosbretabulin IV weekly is the RP2D. Early clinical data suggests clinical activity and stable disease in all but one patient at 3 months. Read full text from ASCO 2019 here.

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Sometimes you just gotta climb that hill!

For further information about the clinical trial, please visit http://www.clinicaltrials.gov, Study NCT03014297

I will get a better picture but this is what they tweeted from ASCO 2019

added 19 Apr 2017

Mateon Therapeutics, Inc. a biopharmaceutical company developing vascular disrupting agents (VDAs) for the treatment of orphan oncology indications, today announced that the Markey Cancer Center at the University of Kentucky has enrolled the first patient into a new phase 1 study of CA4P in combination with everolimus for the treatment of neuroendocrine tumors.

“The combination of CA4P and everolimus has the potential to decrease the ability of tumor cells to recover between CA4P treatment cycles,” stated Lowell B. Anthony, M.D., Professor of Medicine and Chief, Division of Medical Oncology, Markey Cancer Center, University of Kentucky. “This is the first trial testing this hypothesis in neuroendocrine tumors – with CA4P disrupting the existing tumor blood supply and everolimus preventing a new tumor blood supply from re-forming. Our findings from this trial should lead to a larger clinical study once we have identified the optimal dose and schedule for the combination of these two agents.”

Study MCC-2016-088 is designed to demonstrate whether the addition of CA4P to everolimus may improve tumor control without additional toxicity. Everolimus has been approved by the U.S. Food and Drug Administration for the treatment of advanced pancreatic neuroendocrine tumors and progressive gastrointestinal neuroendocrine tumors, among other indications, and is marketed by Novartis under the tradename AFINITOR®. Mateon has previously demonstrated initial evidence of efficacy for CA4P in patients with neuroendocrine tumors when CA4P was provided as a single agent.

Study MCC-2016-088 is being sponsored, funded, and conducted by the Markey Cancer Center, with Mateon providing the investigational drug. The study is designed as a single center, open label, phase 1 clinical trial for patients with grade 1-3 gastroenteropancreatic neuroendocrine tumors. In the first part of the study, up to 15 patients will be treated with everolimus in combination with two different dosing regimens of CA4P to establish appropriate CA4P dosing levels and evaluate the safety of the drug combination.  The second part of the study is designed to enroll 15 additional patients for assessment of additional safety and efficacy data. Patients enrolled in MCC-2016-088 will be treated with CA4P and everolimus for 12 weeks.

For further information about the clinical trial, please visit http://www.clinicaltrials.gov, Study NCT03014297.  (see also ‘added 23 Dec 2016’ below)

added 23 Jan 2017

Mateon Therapeutics, a biopharmaceutical company developing vascular disrupting agents (VDAs) for the treatment of orphan oncology indications, today announced the presentation of final data from Study OX4218 in patients with neuroendocrine tumors (NETs) at a poster session at the ASCO Gastrointestinal Cancers Symposium being held today in San Francisco (20 Jan 17).

Study OX4218 was a multi-center, open label, phase 2 clinical trial to investigate the safety and activity of combretastatin A4-phosphate (CA4P) in the treatment of well-differentiated, low-to-intermediate-grade unresectable, recurrent or metastatic pancreatic or gastrointestinal neuroendocrine tumors/carcinoid (PNETs or GI-NETs) with elevated biomarkers. Following patients’ completion of Study OX4218, patients were eligible to enroll in Study OX4219, a long-term extension study, if they achieved a biomarker or symptom response. In OX4218 patients were treated with CA4P 60 mg/m² on Days 1, 8, and 15 of a 21-day cycle for 3 cycles, and in OX4219 patients received CA4P maintenance on Day 1 of a 21-day cycle until disease progression or up to one year.

A total of 18 patients were enrolled in OX4218. One patient (6%) experienced significant symptomatic improvement as measured by ECOG Status and had a partial response per investigator-assessed RECIST and an additional 7 patients (39%) had stable disease. In addition, a majority of patients (53%) experienced an improvement in patient-reported quality of life.  A statistically significant mean change in biomarkers from baseline, the primary endpoint of the study, was not achieved in OX4218 due to the small sample size along with a high intra- and inter-patient variability observed in the biomarkers. A total of 7 patients were enrolled in OX4219, of which 5 patients (71%) had stable disease, including one that continued for 14 months. The partial response and stable disease analyses, as well as other measures from the trial, suggest that CA4P monotherapy has activity in this indication.

“The results of OX4218 and OX4219 confirm that CA4P monotherapy has efficacy in the indications studied, as we have seen with the investigational drug in a number of other monotherapy trials,” said William D. Schwieterman, M.D., President and Chief Executive Officer of Mateon. “However, we believe that the efficacy of CA4P only becomes compelling when it is used in combination with an anti-angiogenic agent, due to the complementary mechanisms of action for the two agents. Based on the evidence of efficacy observed in this trial, plus an understanding of the benefits of combination therapy, a lead investigator in this trial is sponsoring a 20 patient study in NETs using CA4P in combination with everolimus (AFINITOR®, marketed by Novartis), an anti-angiogenic agent which is already approved and commonly used in this indication.”

Overall CA4P monotherapy was well tolerated. Treatment related adverse events were reported in 77% of subjects. The most common Grade 3-5 AEs (>10%) included: anemia, abdominal pain, fatigue, hypertension, and ALT and AST increases. One Grade 5 adverse event, carcinoid syndrome, was reported and attributed to the underlying disease.

added 23 Dec 2016

There is news of a trial involving this drug which I first published in Jan 2016.  The trial is based at Markey Cancer Centre and is led by Dr Lowell Anthony.  The trial’s primary objective is to establish the maximum tolerated dose of the combination of Everolimus (Afinitor) plus Fosbretabulin in Neuroendocrine Tumors (Grades 1-3) who have progressed after at least one prior regimen for metastatic disease. Read more here.

The original blog published on 10 Jan 2016 follows:

It’s always nice to hear that another treatment for Neuroendocrine Cancer is in the pipeline.  This drug is in the news because it has just been granted designated orphan drug status by the FDA in the US for the treatment of Neuroendocrine Tumours.

My initial thoughts are that it looks promising but it’s very early days.The new drug is formally known as Fosbretabulin Tromethamine or just Fosbretabulin.It also goes by the name of Combretastatin or CA4P which translates to Combretastatin A4-phosphate.In the most basic of terms, it’s a type of vascular disrupting agent (VDA) (note – it’s not chemotherapy).

It appears to be something currently targeted at patients with Advanced Pancreatic or GI Neuroendocrine Tumours with elevated biomarkers.  This is not a new drug and has been around for some years. According to Cancer Research UK, it has already been used for advanced and recurrent ovarian and thyroid cancers.

So how does it work?  The drug makes the cells that line the smallest blood vessels (capillaries) swell up and this has the effect of blocking the blood flow to a tumour. All tumours need a blood supply so that they can get the oxygen and food they need to survive and Neuroendocrine Tumours can be highly vascular. It follows that if the blood flow to a tumour is blocked, there is a chance that it could stop growing or at best kill the tumour (necrosis).  Sounds like the same principles used in Liver Embolization except that this drug has a greater anatomical reach plus a vastly different delivery mechanism via a 10 minute IV infusion.

So why is it a targeted treatment?  The drug will only affect blood vessels that supply cancer cells. Cells lining normal blood vessels contain a protein called actin and this protects the blood vessels from the drug’s effects. Cells lining blood vessels that supply a cancer don’t have actin.

Does it work alongside other treatments?  Interestingly, it appears to be a recommendation to use the drug in combination with anti-angiogenic drugs (i.e. those that can stop the growth of new blood vessels rather than block the blood supply).  Also, according to the manufacturer Mateon, Fosbretabulin has demonstrated broad potential therapeutic value when combined with mainstay oncology modes of treatment including chemotherapy, radiation therapy and the more recent ‘molecularly-targeted therapies’.  In fact if you read the trial addition above dated 23 Dec 16, you will see it’s being tested alongside Everolimus (Afinitor).

So when can we expect to see this drug?  Phase 2 trials were completed at the end of 2016 (results above).  I guess it would still be some years ahead if they wish to proceed. You can see the trial information by clicking here.