As a survivor of bilateral breast cancer (with a deep family history of cancer that one cousin calls “the family curse”) I have a keen interest in advances in cancer therapy.

Classical chemotherapy* targets dividing cells with poison. Cancer cells divide rapidly but so do other cells, such as hair and intestinal cells. This is why chemo is so grueling and also causes hair to fall out.

Modern chemo targets cancer cells specifically based on their mutations. These are much less likely to make patients ill because they aren’t poisons to normal cells. The critical factor is to match the chemo to the specific mutation(s) in the tumor.**

Only a few years ago, clinical trials were proving the concept in practice. Now companies have been formed to test tumors. Once the tumor has been analyzed, the specific chemo can be chosen to target the mutation.

After the cancer treatments (surgery, chemo and/or radiation) the patient is still in danger of recurrence because cancer cells can slip into the bloodstream, hide in bone marrow and lay dormant for years before waking up. (One woman in a breast cancer support group I belong to experienced this recurrence after 17 years and died within a year.)

Until now, there was no way to detect a newly-awakened tumor. PET scans were not correlated with improved survival.

Now the companies that analyze the tumors keep the DNA signature in a database. They can do a blood test to detect circulating tumor DNA by matching it to the original tumor DNA. This extends the business model to a lifelong personalized screen, not just the single point when the tumor is first diagnosed and treated.

There is also the exciting prospect of a personalized mRNA vaccine which can teach the immune system to attack a recurrent tumor. That would be fantastic! Of course, every tumor is different so the vaccine would need to be personalized.

wsj.com - The cancer vaccine gold rush has begun so has the race for picks and shovels

The Cancer Vaccine Gold Rush Has Begun. So Has the Race for Picks and Shovels.
Tempus AI could capture a lucrative slice of Moderna and Merck’s personalized cancer therapy business, with Personalis at the center of the bet

By David Wainer, The Wall Street Journal, Sept. 4, 2026

The excitement surrounding Moderna and Merck’s personalized mRNA cancer vaccine added more than $50 billion in combined market value for the two drug companies. But it is also creating a gold rush in a growing corner of healthcare: tumor sequencing.

Personalized cancer therapies require a genetic road map for each patient. The tumor has to be sequenced to identify the mutations the vaccine should target. If these therapies become blockbusters, the diagnostic companies doing that sequencing could hold a lucrative tollbooth on every dose.

Enter Tempus AI and Personalis, two diagnostics partners suddenly sitting at the center of the opportunity.
[snip a bunch of business dealings]

The strategic prize isn’t just the upfront sequencing fee. It is minimal residual disease, or MRD—a blood test that looks for tiny traces of circulating tumor DNA after treatment, potentially detecting cancer recurrence before it shows up on a scan. ...

After a tumor is sequenced and a therapy given, patients still need to be monitored for signs the cancer has returned. Who better to do that testing than the company that already has the patient’s tumor sequence? Eby sees the mRNA vaccine business as a potential customer-acquisition funnel: The initial sequencing brings the patient into the Tempus ecosystem, while recurring MRD testing could bring them back for years of monitoring...[end quote]

Obviously, the incentive is the potential profits from very expensive personalized tests and treatments.

Moderna’s personally-sequenced vaccine is given as an injection alongside Merck’s Keytruda (pembrolizumab), an established checkpoint inhibitor that prevents cancer cells from hiding from the immune system.

Melanoma Breakthrough: In the landmark Phase 3 INTerpath-001 trial for patients with high-risk stage IIB–IV resected melanoma, the combination met its primary goals. It showed statistically significant improvements in Recurrence-Free Survival (RFS) and Distant Metastasis-Free Survival (DMFS) compared to Keytruda alone.

Phase 2 Long-Term Follow-up: Five-year data from the Phase 2b trial showed a 49% reduction in the risk of recurrence or death when adding intismeran to Keytruda compared to standard monotherapy. [end Gemini quote]

That is simply huge! The 5-year survival for distant spread of malignant melanoma used to be 10% but now can be up to 50% using the combination immunotherapy/ chemotherapy.

Like malignant melanoma, pancreatic cancer is also exceptionally deadly. Trials of the cancer vaccine are already in progress.

This is good news for patients and pharma companies. But these are expensive treatments so it’s bad news for whoever has to pay the bills.

I own Merck stock. Merck makes Keytruda and is deep into deals with the mRNA companies.

Wendy

* I didn’t get chemo because my bilateral tumors were < 1 cm (Stage 1) and I had bilateral mastectomy in 2015.

** Cancer cells can have many mutations. The Moderna mRNA vaccine can be tailored to up to 34 mutations.