ABBV - Sutro: Luveltamab Data At ESMO Signifies Continued ADC Advancement

2023-12-29 16:11:47 ET

Summary

• Positive results achieved from phase 1 dose expansion study using luveltamab tazevibulin for the treatment of patients with FRa-positive endometrial cancer.
• Phase 1 dose expansion study, using luveltamab tazevibulin in FRa-positive endometrial cancer patients, achieved anti-tumor activity in patients who expressed FRa levels >25%.
• Luveltamab tazevibulin has potential to target other cancer types beyond the scope of its competitor AbbVie's ELAHERE, such as: NSCLC, adenocarcinoma, and CBFA2T3-GLIS2 positive AML.
• The endometrial cancer market is expected to reach $24.08 billion by 2032.

Sutro Biopharma ( STRO ) was able to report positive findings from its phase 1 dose expansion study using luveltamab tazevibulin (STRO-002) for the treatment of patients with recurrent folate receptor alpha (FRa) expressing endometrial cancer ((EC)). In the prior article , I noted that this biotech was gearing up to report results from this study at the European Society of Medical Oncology (ESMO) medical conference. Not only were such results reported, but it was found that anti-tumor activity was observed in >25% of these specific EC patients. This established additional proof of concept in the use of Sutro's next-generation antibody-drug conjugates (ADCs). Not only that, but it further establishes proof with respect to ImmunoGen's targeting of FRa with ELAHERE for various types of cancer targets. This can be further refined with the fact that Sutro, like ImmunoGen, was able to effectively use an ADC such as luveltamab tazevibulin to target platinum-resistant ovarian cancer ((PROC)) patients.

This brings me to another reason why I believe that Sutro Biopharma is keen to look at, which is that ImmunoGen was acquired by AbbVie ( ABBV ) for $10.8 billion for ELAHERE. Sutro's luveltamab tazevibulin has competition in place, but it might be able to overcome that issue in that it could go after other types of cancer. This would be beyond the scope of the patient populations that ELAHERE is being developed for. Speaking of which, work is ongoing by Sutro to possibly be in a position to possibly file an IND for luveltamab tazevibulin to initiate the targeting of non-small cell lung cancer (NSCLC) patients. Such an expansion for its drug would allow it to target other indications away from that of which AbbVie is targeting with ELAHERE. Other indications being looked at by this biotech's FRa targeting ADC would be CBFA2T3-GLIS2 positive Acute myeloid leukemia ((AML)) and adenocarcinoma.

Luveltamab Data At ESMO Released Reinforces Next Generation ADC Approach

As I stated above, Sutro Biopharma reported positive findings from its phase 1 dose expansion study , using luveltamab tazevibulin for the treatment of patients with refractory endometrial cancer. Such results were presented at the European Society of Medical Oncology medical conference in October 2023. This ADC drug was able to achieve anti-tumor activity in patients who had Folate Receptor Alpha (FRa) levels > 25% . This was the most significant level observed with FRa, in that patients with this tumor proportion score ((TPS)) percentage had a Partial Response ((PR)) of 29% and a Disease Control Rate ((DCR)) of 86%. This is one cancer indication whereby proof-of-concept has been established that this ADC can have a significant impact on these patients.

The endometrial cancer market is expected to reach $24.08 billion by 2032 . This is a big market opportunity, even if the focus is only on targeting such patients who express FRa. FRa-positive expression is still significantly high in endometrial cancer . This data was pretty much in line with other data from a phase 1 dose expansion study looking at using luveltamab tazevibulin for the treatment of patients with FRa advanced ovarian cancer. Such data also showed that there was a significant benefit observed in patients who had a TPS of > 25% . What's the importance of this other ovarian cancer patient outcome? Well, it pretty much shows the ability to target 80% of these advanced ovarian cancer patients. Having said that, Sutro has been able to do well to not only prove that its own ADC is capable of helping these patients, but the targeting of FRa for ovarian and endometrial cancers is ideal.

With respect to the targeting of the advanced ovarian cancer patient population, it intends to meet with the FDA and European Medicines Agency ((EMA)) regularly to see if it can alter the phase 2/3 REFRaME-O1 study to potentially become a pivotal one. This trial was initiated back in June 2023, but for the time being it is just an advanced type of study design. If this biotech can get the FDA and EMA on board to change this, then it could allow this study to become a registration type. That is, it could be able to file for regulatory approval of luveltalmab tazevibulin for the treatment of patients with platinum-resistant ovarian cancer ((PROC)). Again, there could be potential to possibly improve upon the efficacy in using this ADC to target this patient population through a combination study. That would be to combine luveltalmab tazevibulin together with bevacizumab (AVASTIN) from Roche ( RHHBY ) to target these specific PROC patients.

Big Pharma Interest Could Ignite Upon Continued Advancement

Besides the positive progress that Sutro Biopharma has made in the clinic with its drug luveltalmab tazevibulin for the treatment of patients with platinum-resistant ovarian cancer ((PROC)), there is another reason why I believe this biotech should be watched closely. This would be with respect to the possibility of it ultimately being acquired for its Folate-Receptor alpha (FRa) Antibody-drug conjugate ((ADC)). What makes me make such a bold statement? That is because a big pharmaceutical company, by the name of AbbVie, spent $10.8 billion to acquire ImmunoGen. ImmunoGen is an ADC biotech, which developed and received FDA approval of ELAHERE . This ADC drug was approved by the FDA for the treatment of patients with FRa-positive platinum-resistant ovarian cancer.

AbbVie paid a lot to get its hands on this drug and ImmunoGen's pipeline. My belief is that since Sutro also has a similar ADC targeting FRa, then it too might ultimately be acquired. I believe this could be the case even more so than with just what ImmunoGen was able to accomplish. That would be because Sutro has a goal of taking the use of luveltamab tazevibulin beyond the scope of just FRa endometrial/ovarian cancer patients. It is advancing this drug towards the targeting of other cancer types such as non-small cell lung cancer (NSCLC), adenocarcinoma, and CBFA2T3-GLIS2 positive Acute myeloid leukemia ((AML)). The purpose of mentioning this is to note that while this biotech might have competition with AbbVie in terms of targeting FRa endometrial/ovarian cancer patients, it will be able to target other indications outside the scope of ELAHERE.

Financials

According to the 10-Q SEC Filing , Sutro Biopharma had cash, cash equivalents and marketable securities of $321.1 million as of September 30, 2023. This company is well capitalized for the time being, and I don't foresee the need for it to raise cash until at least towards the 2nd half of 2024. Why is that? For starters, it has an extensive amount of cash on hand. Secondly, it has approximately 0.7 million shares of common stock of Vaxcyte, which equates to about $34 million. The cash on hand, plus the value of shares of Vaxcyte's stock it owns, would mean that it has a projected cash runway into the 1st half of 2025.

Risks To Business

There are several risks that investors should be aware of before investing in Sutro Biopharma. The first risk to consider would be with respect to the use of luveltamab tazevibulin for the treatment of platinum-resistant ovarian cancer ((PROC)) patients in the phase 2/3 REFRaME-O1 study. There is no assurance that this study will turn out to be positive, nor that the intended endpoints will be met with statistical significance. Another aspect to consider is that there is an intention to get this trial moved forward as a possible registration study. This could possibly be done with constructive feedback from either or both the FDA and EMA. However, there is no guarantee that a regulatory filing from either of these agencies will be allowed.

Even after positive data is achieved from the phase 2/3 REFRaME-O1 study, there is no way of knowing if Sutro will be able to file regulatory applications for marketing approval in either of said territories. The second risk to consider would be the use of luveltamab tazevibulin as an ADC targeting other cancer types I mentioned above. It is also being developed for the treatment of patients with non-small cell lung cancer ((NSCLC)), adenocarcinoma, and CBFA2T3-GLIS2 positive Acute myeloid leukemia ((AML)). There is no assurance that this drug will be able to help any of these other cancer patient populations. The third and final risk to consider would be with respect to competition in place. As I stated above, AbbVie with ELAHERE is going to be a major competitor for Sutro Biopharma. Even if Sutro achieves FDA approval of luveltamab tazevibulin for the treatment of patients with platinum-resistant ovarian cancer ((PROC)) patients, there is no guarantee that it will sell well on the market in light of such competition.

Conclusion

Sutro Biopharma has been able to establish proof-of-concept of its own antibody-drug conjugate ((ADC)), known as luveltamab tazevibulin. It has been able to do so in two cancer indication types, which are FRa-positive PROC and also recurrent FRa-positive recurrent endometrial cancer. A good thing about this company is that it can take its ADC targeting approach of FRa-positive cancer patients by going after other indication types. This would be what I noted directly above, with the targeting of other cancers such as NSCLC and adenocarcinoma.

There is no way of knowing whether or not this drug will be capable of being able to help these other patient populations, but at least these are other shots on goal for it. Lastly, there are two other ADCs being developed in the pipeline with added potential as well. The first of which is STRO-003, which is being advanced for the targeting of ROR1 expressing solid and hematological malignancies. The second one, which is known as STRO-004, is a tissue factor ADC being developed for the treatment of patients with solid tumors. IND filings to initiate clinical testing for both of these candidates are expected in 2024 and 2025, respectively.

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