Cardiff Oncology: Risky Investment


  • Despite producing decent data, the stock has kept falling.
  • Today it is in the penny stock zone, and we do not recommend penny stocks as investments.
  • However, Pfizer's small stake is a silver lining.
  • Looking for a portfolio of ideas like this one? Members of The Total Pharma Tracker get exclusive access to our model portfolio. Learn More »

Business on Wall Street in Manhattan

Pgiam/iStock via Getty Images

Cardiff Oncology (NASDAQ:CRDF) is in the penny stock zone today; a highly risky stock that I covered twice before. Their lead and only asset is onvansertib, an oral and highly-selective inhibitor of Polo-like Kinase 1 (PLK1). And therein lies the problem. PLK1 inhibitors have unresolved safety issues.

A 2019 paper I read says the following:

First, most of the PLK1 inhibitors achieved therapeutic effects only when doses exceeded toxic limits.

And to address that issue, they recommend:

First of all, research should address how to foster the potency of PLK1-targeting drugs to avoid drug toxicity. This could be attained through developing probes with higher affinity and enhanced accessibility to PLK1 molecules. Concordantly, improving specificity of PLK1 inhibitors is equally important as it can reduce the therapeutic doses required via confining the drug to the pursued target. Furthermore, higher specificity can minimize the off-target toxicities.

Now, besides onvansertib, there are at least two other major PLK1 inhibitors - rigosertib and volasertib. Volasertib is an old molecule; in phase 1 trials, its toxicity profile was as follows:

Reversible hematotoxicity was the main side effect with thrombocytopenia, neutropenia and febrile neutropenia constituting the dose limiting toxicities. Anemia in 22% (grade 3: 8%), neutropenia in 15% (grade 3/4: 14%), thrombocytopenia in 14% (grade 3/4: 14%) and fatigue in 15% (all grade 1/2) of patients were the most frequent drug-related side effects.

For Cardiff to get ahead of the pack, it needed to demonstrate superlative efficacy data for its Phase Ib/II trial in KRAS-mutated mCRC trial with a manageable safety profile.

According to Fierce:

However, Cardiff thinks it can carve out a lane in the KRAS cancer market. In early phase 1b/2 data revealed in September, onvansertib spurred an initial partial response in eight of 19 patients, or 42%, who got the middle dose and could be evaluated as of the cut-off date. Those phase 1b/2 data compare to an objective response rate of 5% to 13% across historical controls of patients receiving standard of care, the biotech said at the time.

Compare this to data from Amgen’s Lumakras and mirati’s adagrasib:

The group yesterday boldly pointed to Mirati and Amgen’s Kras inhibitors, adagrasib and Lumakras, which in colorectal cancer have respectively yielded ORRs of just 17% and 7%.

However, what has spooked investors is that in the uncontrolled trial here, onvansertib’s efficacy seems to have waned over the months. Here’s a chart from Evaluate that shows how:


Data cutoff

Responses (ORR)

Confirmed responses (ORR)

28 Apr 2020 (AACR)

24 Jan 2020

3/8 PR (38%)


17 Sep 2020 (Esmo)

4 May 2020

5/11 PR (45%)

4/11 PR (36%)

15 Jan 2021 (Asco-GI)

1 Nov 2020

5/12 PR (42%)

4/12 PR (33%)

12 Apr 2021


7/18 PR (39%)

4/18 PR (22%)

8 Sep 2021

2 Jul 2021

12/32 PR (38%)

10/32 PR (31%)

2 Jul 2021 at RP2D

8/19 PR (42%)

7/19 PR (37%)

18 Jan 2022 (Asco-GI)

3 Dec 2021*

17/48; 1 CR, others PR (35%)*

13/48; 1 CR, others PR (27%)

3 Dec 2021 at RP2D*

12/35; 1 CR, others PR (34%)*

10/35; 1 CR, others PR (29%)

Data still looks better than competing KRAS molecules, however the distinct tapering down of efficacy over the months is quite noticeable.

Pfizer must have seen something here the market isn’t seeing; in November last year, it paid $15mn to Cardiff as part of a deal to get a first look at the data:

In connection with the equity investment, Adam Schayowitz, Ph.D., MBA, Vice President & Medicine Team Group Lead for Breast Cancer, Colorectal Cancer and Melanoma at Pfizer, will join Cardiff Oncology's Scientific Advisory Board, once formed. Dr. Schayowitz commented, "Pfizer strives to make a meaningful difference for people living with cancer through the advancement of innovative therapies, and we believe that collaboration and strategic investments are key to achieving this goal. We are pleased to be supporting Cardiff Oncology and look forward to potential new approaches to addressing cancers with pressing unmet needs."

Financials And Risk Discussion

CRDF has a market cap of just $57mn and a cash balance of $129mn, so the market is severely bearish this company. The company spent $11mn in the previous quarter, which gives us a long runway at that rate.

The trouble with trial data with this company is that available data are only from small, open label trials. Until the market sees much more rigorous data from a pivotal trial, I believe it will remain suspicious.


Some bullish investors will see Pfizer’s $15mn as a clarion call for buying CRDF. Let’s look at it another way. $15mn is to Pfizer what $500 is to us ordinary mortals, give or take a few hundred dollars. So yes, Pfizer’s interest is a vote of confidence, but it is an extremely cautious, small vote. We should really bear that in mind.

About the TPT service

Thanks for reading. At the Total Pharma Tracker, we offer the following:-

Our Android app and website features a set of tools for DIY investors, including a work-in-progress software where you can enter any ticker and get extensive curated research material. 

For investors requiring hands-on support, our in-house experts go through our tools and find the best investible stocks, complete with buy/sell strategies and alerts.

Sign up now for our free trial, request access to our tools, and find out, at no cost to you, what we can do for you. 

This article was written by

Avisol Capital Partners profile picture
Cautious, low key, disciplined investing in biopharma stocks
Avisol Capital Partners runs the Total Pharma Tracker Seeking Alpha Marketplace service. This is managed by Dr Asok Dutta, BVScAH and Dr Udaya Kumar Maiya, MD Oncologist. The service offers end-to-end research on both investing and trading ideas everyday, and includes a 150-stock watchlist and two 40-stock model portfolios that are continuously tracked.

Dr Dutta is a retired veterinary surgeon. He has over 40 years experience in the industry. Dr Maiya is a well-known oncologist who has 30 years in the medical field, including as Medical Director of various healthcare institutions. Both doctors are also avid private investors. They are assisted by a number of finance professionals in developing this service.

If you want to check out our service, go here -

Disclaimer - we are not investment advisors.

Disclosure: I/we have no stock, option or similar derivative position in any of the companies mentioned, and no plans to initiate any such positions within the next 72 hours. I wrote this article myself, and it expresses my own opinions. I am not receiving compensation for it (other than from Seeking Alpha). I have no business relationship with any company whose stock is mentioned in this article.

To ensure this doesn’t happen in the future, please enable Javascript and cookies in your browser.
Is this happening to you frequently? Please report it on our feedback forum.
If you have an ad-blocker enabled you may be blocked from proceeding. Please disable your ad-blocker and refresh.